Oglethorpe to its Members varied slightly. There was however, a decrease in MWhs sold to Members primarily due to the termination, effective March 31, 2006, of an agreement to purchase capacity and energy from Georgia Power CorporationCompany (GPC). at a favorable cost. This decrease was primarily offset somewhat by an increase in MWhs generated and sold to Members. For further discussion regarding purchased power costs and the increase in generation, see "Operating Expenses" below.

The components of Member revenues for the three months and nine months ended March 31,September 30, 2007 and 2006 were as follows (amounts in thousands except for cents per kilowatt hour):

Capacity revenues for the three-month periodand nine-month periods ended March 31,September 30, 2007 increased 2.1%2.9% and 3.9% compared to the same periodperiods of 2006. Capacity revenues as budgeted and billed for the nine-month period ended September 30, 2007 reflect reducedlower collections of approximately $1.3$3.8 million due to the termination of the GPC power purchase agreement as budgeted.effective March 31, 2006. Capacity revenues as budgeted and billed for the nine-month period ended September 30, 2006 reflect reducedlower collections from Members ($7.0 million) as budgeted. Theof $20.9 million. Collections from Members were lower in 2006 reduced revenue collections are related to offset a portion of the gain on sale of SO₂allowances as discussed above.in 2006. Energy revenues were 2.9% lower6.0% and 5.5% higher for the three-month periodand nine-month periods ended March 31,September 30, 2007 compared to the same periodperiods of 2006. Oglethorpe's average energy revenue per MWh from sales to Members was 2.0%3.8% and 6.0% higher for the current quarterperiods of 2007 as compared to the same periodperiods of 2006. The decreaseincrease in energy revenues for the current period ofthree months and nine months ended September 30, 2007 was primarily due to decreasesan increase in the pass through of higher fuel costs. For the nine-month period ended September 30, 2007 the increase in higher fuel costs was offset somewhat by the pass through of lower purchased power costs offset somewhat by higher fuel costs. For a discussion onof fuel costs and purchased power costs and fuel costs see "Operating Expenses""Operating Expenses" below.

Operating Expenses

Operating expenses for the three-month periodand nine-month periods ended March 31,September 30, 2007 (excluding the gain on the sale of SO₂ allowances of $0$0.4 million for year-to-date 2007 and $38.8$39.5 million for the three monthsame period ended March 31, 2007 andof 2006, respectively,) were 7.3% lowerincreased 5.2% and 1.5% compared to the same periodperiods of 2006. The decreaseincrease in operating expenses for the three-monthcurrent quarter of 2007 compared to the same quarter of 2006 was primarily due to higher fuel costs and higher production expenses. The increase in operating expenses for the nine-month period ended March 31,September 30, 2007 compared to the same period of 2006 was primarily due to decreasesincreases in fuel costs and production expenses offset somewhat by lower purchased power and depreciation expenses offset somewhat by increases in fuel and accretion costs.expenses.

For the three-month periodand nine-month periods ended March 31,September 30, 2007 compared to the same periodperiods of 2006, total fuel costs increased 21.8%7.6% and 13.1% while total generation increased 2.5%. and 1.6%, respectively. Average fuel costs per MWh increased 18.8%5.0% and 11.3% in the current periods of 2007 compared to the same periodperiods of 2006. The increase in total and average fuel costs for the three-month periodand nine-month periods ended March 31,September 30, 2007 as compared to the same quarterperiods of 2006 resulted primarily from increased generation at theof higher cost natural gas-fired generation from both the Chattahoochee energy facility and, to a lesser degree, from the Talbot energy facility.

Total purchased powerProduction costs decreased 43.6%increased 9.8% for the three-month period ended March 31,September 30, 2007 compared to the same period of 2006. Purchased MWhsThe increase was primarily due to increased amortization of deferred nuclear refueling outage costs and increased amortization of deferred operations and maintenance (O&M) outage costs for coal-fired generation plants in 2007 compared to 2006. The increase in O&M expenses is also partly attributable to higher expenses at Plant Wansley for Selective Catalytic Reduction (SCR) operations. In addition, administrative and general (A&G) expenses increased by 25.7% (or $1.6 million) partly due to timing of expenses incurred from various membership organizations and partly due to increases in administrative support services from Georgia System Operations Company (GSOC), professional services and payroll expenses.

Total purchased power costs decreased 61.4%5.0% and 17.0% for the three monthsthree-month and nine-month periods ended March 31,September 30, 2007 compared to the same periodperiods of 2006. Purchased MWhs decreased 5.5% and 30.0% for the three months and nine months ended September 30, 2007 compared to the same periods of 2006. The average cost per MWh of total purchased power increased 46.2%0.6% and 18.5% for the three months and nine months ended March 31,September 30, 2007 compared to the same periodperiods of 2006.

Purchased power costs were as follows:

Purchased power capacity costs varied slightly in the current quarter of 2007 compared to the same quarter of 2006 and decreased 32.2%13.0% for the threenine months ended March 31,September 30, 2007 as compared to the same period of 2006. Purchased power energy costs for the three-month periodand nine-month periods ended March 31,September 30, 2007 were 47.8% lowerdecreased 6.4% and 18.3% compared to the same periodperiods of 2006. The decrease in purchased power capacity and energy costs for the nine months ended September 30, 2007 compared to the same period of 2006 resulted primarily from the decrease in purchased MWhs, which in turn resulted primarily from the termination of the GPC agreement, effective March 31, 2006, as discussed above. The average cost of purchased power energy decreased 1.0% and increased 16.7% for the three-month and six-month periods ended September 30, 2007 compared to the same periods of 2006. Purchased power energy costs, purchased MWhs and average cost of energy per MWh varied slightly for the current quarter of 2007 compared to the same quarter of 2006 resulted primarily from the termination of the GPC agreement as discussed above.2006. The average costdecrease in purchased power energy costs and volume of purchased power MWhs along with the increase in average energy forcost per MWh during the three-monthnine-month period ended March 31,September 30, 2007 was 35.3% higher compared to the same period of 2006. The2006 was primarily due to the termination of the GPC purchasepurchased power agreement with(with its favorable energy cost to Oglethorpe), effective March 31, 2006. The decrease in MWhs acquired under Oglethorpe's energy replacement program which replaces power from Oglethorpe was the primary contributorowned generation facilities with lower price spot market purchased power energy also contributed to the increasedecrease in purchased power energy costs and to the average energy cost per MWh.volume of purchased power MWhs.

Accretion expense represents the change in the asset retirement obligations due to the passage of time. For nuclear decommissioning, Oglethorpe records a regulatory asset or liability for the timing difference in accretion recognized under SFAS No. 143, "Accounting for Asset Retirement Obligations", compared to the expense recovered for ratemaking purposes. The accretion expense recognized is equal to the lesser of the earnings from both the decommissioning trust fund and the internal

decommissioning fund.fund or the ARO nuclear decommissioning expenses to be recognized under FAS No. 143. The earnings in the three-month and nine-month periods ended September 30, 2007 were $852,000$0.9 million higher and $1.5 million lower than in the same periodperiods of 2006. As a result, accretion expense increased 51.4% and decreased 4.9%, respectively, during the three and nine months ended September 30, 2007 as compared to the same periods of 2006.

Depreciation and amortization expense decreased 23.8%9.3% (or $11.4$11.2 million) for the three-monthnine-month period ended March 31,September 30, 2007 compared to the same period of 2006. Depreciation and amortization expenses in 20062007 were higherlower primarily as a resultbecause of Oglethorpe's decision to accelerateaccelerated amortization of deferred amortization of capital leases taken in 2006 in order to offset a portion of the gain from the 2006 sale of SO₂ allowances. Depreciation and amortization expense remained relatively flat during that period.the three months ended September 30, 2007 as compared to the same period of 2006.

Other Income

Investment income increased 23.9%40.0% (or $2.2$2.7 million) and 11.4% (or $3.3 million) in the current three-month periodand nine-month periods in 2007 compared to the same periodperiods of 2006. The increase infor the first quarter ofthree months and nine months ended September 30, 2007 compared to the same quarterperiods of 2006 resulted partlyprimarily from an increase in earnings from Oglethorpe's decommissioning trust fund established in accordance with the regulations of the Nuclear Regulatory Commission (NRC) and partly due to higherincreased interest earnings on cash and cash equivalent investments principally as a result of higher average balances on these investments.investment balances. The higher investment balances resulted primarily from cash generated due to the issuance of additional debt as discussed in interest charges"Interest Charges" below. ThisThe increase to investment income for the nine months ended September 30, 2007 was offset somewhat partly by the elimination of earnings from funds deposited in the Rural Utilities Service ("RUS")(RUS) Cushion of Credit Account. These fundsAccount and partly from lower earnings from the decommissioning trust fund as discussed above. Funds in the Cushion of Credit Account were utilized to pay debt service costs and as of September 30, 2006, there were no remaining deposits invested in the account; therefore, there willhas not bebeen any additional income relative to these investments in subsequent periods.

Interest Charges

Interest on long-term debt and capital leases increased by 5.2% (or $2.6 million)5.0% and 5.1% in the three months and nine months ended March 31,September 30, 2007 compared to the same periodperiods of 2006. This increase resulted primarily from the issuance of $300 million in first mortgage bonds in October 2006; the proceeds are being used to fund the installation of environmental controls facilities at Plant Scherer, one of Oglethorpe's coal-fired generating plants, and for general corporate purposes.

Balance Sheet Analysis as of March 31,September 30, 2007

General

Assets

Property additions for the threenine months ended March 31,September 30, 2007 totaled $39.6$123.1 million. Included in this total were expenditures of approximately $9$26 million for nuclear fuel and approximately $9$53 million for environmental control projects. The remaining expenditures were primarily for normal additions and replacements to existing generation facilities.

Construction work in progress increased by $17.8$71.4 million in the threenine months ended March 31,September 30, 2007, primarily due to costs incurred for various replacement and improvement projects (including environmental control) at existing generation facilities.

The $15.0 million decrease in long-term investments was principally due to a $21.2 million decrease in the holdings of auction rate securities. The funds were primarily re-invested in commercial paper, which is short-term in nature.

Cash and cash equivalents decreased $54.1$97.4 million principally due to the timing of certain debtprincipal and interest payments, property additions and payments to GPC, property tax payments and property additions.GPC.

Restricted cash and cash equivalents at December 31, 2006 representrepresented a portion of the proceeds obtained from the refinancing of certain indebtedness associated with pollution control bonds (PCBs) in October 2006. These proceeds, which were on deposit with a trustee, were subsequently used in the first quarter of 2007 to pay principal related to the refinanced PCB debt that matured in January 2007.

Receivables increased $31.3 million, or 34.2%. The increase was due in part to an increase of approximately $13.3 million in energy revenue (September 2007 vs. December 2006), which was largely a result of increased generation at the natural gas fired plants. In addition, the December 31, 2006 receivables balance included approximately $10.1 million of credits available to the Members for a Board approved reduction to 2006 revenue requirements. These credits were realized by the Members during the first quarter of 2007. This was the primary cause of the $12.7 million increase in receivables.

Prepayments and other current assets decreased by 29.5% primarily due to the amortization of prepaid insurance balances.

Deferred outage costs increased $11.2$4.5 million (net of amortization), or 43.4%17.6%, largely as a result of the deferral of approximately $8.8$9.0 million of refueling outage costs incurred at Plant Hatch Unit No. 2 and $7.2$11.3 million at Plant Vogtle Unit No. 2 during the first quarter ofnine months ended September 30, 2007. In addition, approximately $1.9 million was deferred for scheduled major maintenance costs at Plant Wansley Unit No. 1.1 and $5.6 million at Plant Scherer Unit No. 2. Deferred outage costs are amortized over the plant's operating cycle.

As a result of the adoption of FIN 48, Oglethorpe has reversed the valuation allowance of a $96$72 million deferred tax asset. For further discussion regarding the deferred tax asset see Note (B)B of the Notes to Unaudited Condensed Financial Statements.

Other deferred charges increased $2.4 million primarily due to a $1.9 million increase in equipment prepayments to GPC. These prepayments are associated with refueling outages at Plant Hatch and Plant Vogtle.

Equity and Liabilities

Accounts payableLong-term debt and capital leases due within one year decreased 18.4%52.2%, or $5.8 million,$122.4 million. The decrease was primarily as a result of a $3.0 million decrease in the purchasereclassification of natural gas in March 2007 as comparedcertain Federal Financing Bank (FFB) and Pollution Control Bond (PCB) debt to December 2006. This decreaselong-term debt. The reclassification was due in part to decreased generation at the natural gas fired plants. In addition, $1.0maturity extension of $428 million of certain FFB debt in May 2007. In October 2007, Oglethorpe also refinanced $454 million of certain FFB debt and $182 million of certain PCB debt. The short-term portions of these debts were also reclassified to long-term debt in accordance with SFAS No. 6, "Classification of Short-term Obligations Expected to be Refinanced". For further discussion regarding the decrease is attributed to a reduction in off system purchases.extension of the FFB debt maturities and FFB debt prepayment, see "Financings" below.

The decrease in accrued interest was largely due to the timing of a principal and interest payment for the Plant Scherer Unit No. 2 capital lease obligation. The December 31, 2006 accrued interest balance included an amount for the semi-annual lease payment that was due on January 2, 2007. These payments are made on a semi-annual basis, and2007, while the balance at March 31,September 30, 2007 includesincluded only three months of accrued interest.

Accrued and withheld taxes decreased $10.7 million as a result of payments made related to 2006 property taxes, which were paid when due. The decrease was net of monthly accruals for 2007 property taxes.

Other current liabilities decreased by $4.7 million or 51.7%. The decrease was due in large part to a $2.1 million decrease in accrued payroll charges as a result of the payment of 2006 performance-based payroll charges. In addition, miscellaneous accounts payable accruals decreased by $1.3 million, and the liability associated with the unrealized loss for natural gas hedges decreased by $1.1 million. These hedges were in a net gain position at March 31, 2007, and a corresponding asset was recorded.

As a result of a $1.9$5.5 million increase in the unrealized gain associated with the nuclear decommissioning fund and an additional $891,000$1.3 million of accretion expense recorded as a result of decommissioning fund earnings, the deferred ARO creditsliability associated with asset retirement obligations increased by $2.9$7.3 million. For further discussion regarding accretion expense, see "Operating Expenses""Operating Expenses" above.

As a result of the adoption of FIN 48, Oglethorpe has recorded a $96$72 million long-term contingent tax liability. For further discussion regarding the long-term contingent tax liability see Note (B)B of the Notes to Unaudited Condensed Financial Statements.

Other deferred credits and liabilities increased primarily due to a $4.5 million increase in liabilities associated with payments made to Oglethorpe by its Members. Approximately $2.2 million of the

increase is associated with funding the future overhaul of the combustion turbine plants. An additional $2.3 million is associated with the funding of future debt payments.

Financial Condition

Capital Requirements and Liquidity and Sources of Capital

Environmental MattersCapital Requirements

Oglethorpe's future capital expenditures depend in part on future environmental regulations, including future implementation of existing laws and regulations and how Oglethorpe and the other co-owners of coal-fired Plants Scherer and Wansley choose to comply with these regulations, once finalized. See "Management's DiscussionRegulations recently adopted by the Georgia Environmental Protection Division specify certain environmental control equipment that must be added to Georgia electric generating units, and Analysis of Financial Conditionby specific dates, including Plants Scherer and Results of Operations—Wansley. As described in "MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS—Financial Condition—Capital Requirements" in Oglethorpe's Annual Report on Form 10-K for the fiscal year ended December 31, 2006, Oglethorpe forecasted expenditures of $252 million for environmental compliance in 2007-2009. Oglethorpe also reported the likelihood of being required to spend $400 million to $600 million beyond 2009, in anticipation of finalization of regulations. As design work has continued to determine how best to retrofit the units with the required equipment, and as the construction environment is now being evaluated, the estimated cost to install these retrofits continues to be being refined. Current indications are that the capital expenditures required beyond 2009 will exceed $600 million, maybe by as much as $200 million to $300 million. Large construction projects such as these entail certain risks, as described in Item 1A of Oglethorpe's Annual Report on Form 10-K for the fiscal year ended December 31, 2006. There can be no assurance that the cost of compliance with these regulations will not be higher, nor that future regulations will not require additional reductions in emissions or earlier compliance. See Note E of the Notes to Unaudited Condensed Financial Statements for more information on environmental compliance matters.

Liquidity

As of March 31,September 30, 2007, Oglethorpe had $770$876 million of unrestricted available liquidity to meet short-term cash needs and liquidity requirements. This liquidity consisted of (i) approximately $370$326 million in cash and cash equivalents, and (ii) $400$550 million available under three committed working capital line of credit facilities (see discussion below).

Oglethorpe also had $48 million invested in auction rate securities at March 31, 2007. These securities have maturities in excess of one year and as such are classified as long-term investments. However, most of these securities re-price in auctions that occur every 35 days or less, and Oglethorpe could seek to liquidate these securities at the end of any auction period.facilities.

Oglethorpe has in place a $300five-year $450 million committed working capital line of credit supporting its commercial paper program that matures in July 2012. The line of credit contains a financial covenant requiring Oglethorpe to maintain patronage capital of at least $400 million, and at September 2007.30, 2007, Oglethorpe has planshad patronage capital in excess of $516 million. The facility also contains an additional covenant limiting Oglethorpe's secured indebtedness to renew this facility priorno more than $8.5 billion and its unsecured indebtedness to its expiration date, and may increase the size of the facility by $100 million or more. no more than $4.0 billion. Oglethorpe's current debt levels are well below these thresholds.

Oglethorpe also has in place two $50 million committed lines of credit, one with National Rural Utilities Cooperative Finance Corporation ("CFC") that matures in October 2008, and one with CoBank, ACB that matures in November 2008. Oglethorpe expects to renew the CFC and CoBank credit facilities, as needed, prior to their respective expiration dates.

There are currently no amounts outstanding under any of the three committed credit facilities discussed above.

Oglethorpe also had $40 million invested in auction rate securities at September 30, 2007. These securities have maturities in excess of one year and as such are classified as long-term investments. However, most of these three facilities.securities re-price in auctions that occur every 35 days or less, and Oglethorpe could seek to liquidate these securities at the end of any auction period.

Planned Financings

Oglethorpe has embarked on a program to refinance or otherwise reamortize a portion of its FFB and PCB debt to extend the maturities of this debt in connection with the extension, in 2005, of its Member wholesale power contracts from 2025 to 2050. In connection with this program, on October 3, 2007 Oglethorpe issued $500,000,000 of Series 2007 First Mortgage Bonds, the proceeds of which were used to prepay approximately $450 million of existing FFB debt and for other general purposes. This new fixed rate debt is subject to mandatory sinking fund redemptions occurring in 2024 to 2030, with a final maturity in 2031.

Also in connection with the debt reamortization program, will include a fallon October 25, 2007 refinancing of approximatelyOglethorpe issued $182 million of Series 2007 PCB debt, which was used to refinance a like amount of existing PCB debt, including $22 million scheduled to mature on January 1, 2008,

Also Georgia Transmission Corporation (GTC) elected to participate in connection with this program, in mid-2007 Oglethorpe expectsrefunding and assumed an obligation to extend the maturities on approximately $430pay $3.7 million of existing FFB debt advances underthe Burke Series 2007A debt. See "MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS—Financial Condition—Off-Balance Sheet Arrangements—GTC Debt Assumption" in Oglethorpe's Annual Report on Form 10-K for the fiscal year ended December 31, 2006.

In September 2007, the RUS approved a new option being provided by RUS which allows$442 million loan for a one-time extension of FFB debt while maintaining the current interest rateOglethorpe representing two outstanding loan applications that were pending. Oglethorpe does not anticipate closing on the debt. When completed, Oglethorpe will achieve maturity extensions of between 13this loan and 20 years on these FFB advances in connection with this transaction.advancing any funds thereunder until mid-2008.

For more detailed information on the transactions described above, as well as additional information on other planned financings of Oglethorpe (including loan applications that are pending with the RUS),regarding Oglethorpe's financing plans, see "Management's Discussion and Analysis of Financial Condition and Results of Operations—"MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS—Financial Condition—Financing Activities" in Oglethorpe's Annual Report on Form 10-K for the fiscal year ended December 31, 2006.

Critical Accounting Policy

Oglethorpe's critical accounting policypolicies have not changed from the policy reported in Oglethorpe's 2006 Annual Report on Form 10-K for the fiscal year ended Dec. 31, 2006 except for the estimate recorded in conjunction with the adoption of FIN 48. See Note B of the Notes to Unaudited Condensed Financial Statements for further discussion.

New Accounting Interpretation and Standards

For discussion of FIN 48 and SFAS No. 159 and 157 see Notes B and Note C of the Notes to Unaudited Condensed Financial Statements.

Item 3. Quantitative and Qualitative Disclosures About Market Risk

Oglethorpe's market risks have not changed materially from the risks reported in Oglethorpe's 2006 Annual Report on Form 10-K.10-K for the fiscal year ended Dec. 31, 2006.

Item 4. Controls and Procedures

As of March 31,September 30, 2007, Oglethorpe had carried out an evaluation, under the supervision and with the participation of its management, including its President and Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of its disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended). Based on this evaluation, the President and Chief Executive Officer and the Chief Financial Officer concluded that Oglethorpe's disclosure controls and procedures are effective.

There have been no changes in Oglethorpe's internal control over financial reporting or other factors that occurred during the quarter ended March 31,September 30, 2007 that have materially affected, or are reasonably likely to materially affect, Oglethorpe's internal control over financial reporting.

PART II — OTHER INFORMATION

Item 1. Legal Proceedings

Environmental Matters

For information about legal and regulatory proceedings regarding environmental matters that could have an effect on Oglethorpe, see Note D toE of the Notes to Unaudited Condensed Financial Statements (Unaudited).Statements.

Item 1A. Risk Factors

There have not been any material changes in Oglethorpe's risk factors from those disclosed in Item 1A of Oglethorpe's Annual Report on Form 10-K for the fiscal year ended December 31, 2006.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds.
Proceeds

Not Applicable.

Item 3. Defaults upon Senior Securities

Not Applicable.

Item 4. Submission of Matters to a Vote of Security Holders

Not Applicable.

Item 5. Other Information

None.Not Applicable.

Item 6. Exhibits

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

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PART I—FINANCIAL INFORMATION
Item 1. Financial Statements
Oglethorpe Power Corporation Notes to Unaudited Condensed Balance Sheets March 31, 2007 and December 31, 2006

Oglethorpe Power Corporation Condensed Balance Sheets March 31, 2007 and December 31, 2006

Oglethorpe Power Corporation CondensedFinancial Statements of Revenues and Expenses (Unaudited) For the Three Months Ended March 31,September 30, 2007 and 2006

Oglethorpe Power Corporation Condensed Statements of Patronage Capital and Membership Fees and Accumulated Other Comprehensive Loss (Unaudited) For the Three Months Ended March 31, 2007 and 2006

Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations
Item 3. Quantitative and Qualitative Disclosures About Market Risk
Item 4. Controls and Procedures

PART II — OTHER INFORMATION
Item 1. Legal Proceedings
Item 1A. Risk Factors
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds.
Item 3. Defaults upon Senior Securities
Item 4. Submission of Matters to a Vote of Security Holders
Item 5. Other Information
Item 6. Exhibits