UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

For the Quarterly Period Ended September 30, 2011March 31, 2012

or

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  þ    No  ¨.

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  þ    No  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See definition of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act).    Yes  ¨    No  þ.

The number of shares outstanding of each registrant’s common stock as of September 30, 2011March 31, 2012 was:

TABLE OF CONTENTS

				Page No.
		11. Plant Retirements7. Derivative Financial Instruments			9372
		12. Earnings Per Share8. Debt and EquityCredit Agreements			88
		9. Income Taxes			91
		10. Nuclear Decommissioning			94
		13. Commitments and Contingencies11. Retirement Benefits			9596
		12. Plant Retirements			99
		13. Stock-Based Compensation Plans			100
		14. Supplemental Financial InformationEarnings Per Share and Equity			106103
		15. Commitments and Contingencies			104
		16. Supplemental Financial Information			119
		17. Segment Information			112123
ITEM 2.		MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS			115128
		Exelon Corporation			115128
		General			115128
		Executive Overview			115129
		Critical Accounting Policies and Estimates			133142
		Results of Operations			134143
		Liquidity and Capital Resources			155164
		Exelon Generation Company, LLCContractual Obligations and Off-Balance Sheet Arrangements			166
		Commonwealth Edison Company			167
		PECO Energy Company			169176
ITEM 3.		QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK			171177
ITEM 4.		CONTROLS AND PROCEDURES			179185
PART II.		OTHER INFORMATION			180187
ITEM 1.		LEGAL PROCEEDINGS			180187
ITEM 1A.		RISK FACTORS			180187
ITEM 4.		MINE SAFETY DISCLOSURES			188
ITEM 6.		EXHIBITS			185189
SIGNATURES					186192
		Exelon Corporation			186192
		Exelon Generation Company, LLC			186192
		Commonwealth Edison Company			187192
		PECO Energy Company			187193
		Baltimore Gas and Electric Company			193
CERTIFICATION EXHIBITS					188194
		Exelon Corporation			188, 189194, 204
		Exelon Generation Company, LLC			190, 191196, 206
		Commonwealth Edison Company			192, 193198, 208
		PECO Energy Company			194, 195200, 210
		Baltimore Gas and Electric Company			202, 212

GLOSSARY OF TERMS AND ABBREVIATIONS
Exelon Corporation and Related Entities
Exelon		Exelon Corporation
Generation		Exelon Generation Company, LLC
ComEd		Commonwealth Edison Company
PECO		PECO Energy Company
BGE		Baltimore Gas and Electric Company
BSC		Exelon Business Services Company, LLC
Exelon Corporate		Exelon’s holding company
CENG		Constellation Energy Nuclear Group, LLC
Constellation		Constellation Energy Group, Inc.
Exelon Transmission Company		Exelon Transmission Company, LLC
Exelon Wind		Exelon Wind, LLC and Exelon Generation AcquisitionAcquisitions Company, LLC
Enterprises		Exelon Enterprises Company, LLC
Ventures		Exelon Ventures Company, LLC
AmerGen		AmerGen Energy Company, LLC
PEC L.P.BondCo		PECO Energy Capital, L.P.RSB BondCo LLC
PECO Trust III		PECO Capital Trust III
PECO Trust IV		PECO Energy Capital Trust IV
PETT		PECO Energy Transition Trust
Registrants		Exelon, Generation, ComEd, PECO and PECO,BGE, collectively
Other Terms and Abbreviations
Note “    ” of the 2010Exelon 2011 Form 10-K		Reference to specific Combined Note to Consolidated Financial Statements within Exelon’s 20102011 Annual Report on Form 10-K
1998 restructuring settlement		PECO’s 1998 settlement of its restructuring case mandated by the Competition Act
Act 12911		Pennsylvania Act 12911 of 20082012
AEC		Alternative Energy Credit that is issued for each megawatt hour of generation from a qualified alternative energy source
AEPS ActAESO		Pennsylvania Alternative Energy Portfolio Standards Act of 2004Alberta Electric Systems Operator
AFUDC		Allowance for Funds Used During Construction
ALJ		Administrative Law Judge
AMI		Advanced Metering Infrastructure
ARC		Asset Retirement Cost
ARO		Asset Retirement Obligation
ARP		Title IV Acid Rain Program
ARRA of 2009		American Recovery and Reinvestment Act of 2009
ASLB		Atomic Safety Licensing Board
Block contracts		Forward Purchase Energy Block Contracts
CAIR		Clean Air Interstate Rule
CAMR		Federal Clean Air Mercury Rule
CERCLA		Comprehensive Environmental Response, Compensation and Liability Act of 1980, as amended
CFLClean Air Act		Compact Fluorescent LightClean Air Act of 1963, as amended
Clean Water Act		Federal Water Pollution Control Amendments of 1972, as amended
Competition Act		Pennsylvania Electricity Generation Customer Choice and Competition Act of 1996
CPICSAPR		Consumer Price IndexCross-State Air Pollution Rule
CTC		Competitive Transition Charge
DOE		United States Department of Energy
DOJ		United States Department of Justice
DSP Program		Default Service Provider Program
EDF		Electricite de France SA
EE&C		Energy Efficiency and Conservation/Demand Response
EGS		Electric Generation Supplier
EIMA		Illinois Senate Bill 1652 and Illinois House Bill 3036
EPA		United States Environmental Protection Agency
ERCOT		Electric Reliability Council of Texas
ERISA		Employee Retirement Income Security Act, as amended
EROA		Expected Rate of Return on Assets

GLOSSARY OF TERMS AND ABBREVIATIONS
Exelon Corporation and Related Entities
Other Terms and Abbreviations
ERCOT		Electric Reliability Council of Texas
ESPPERISA		Employee Stock Purchase PlanRetirement Income Security Act of 1974, as amended
EROA		Expected Rate of Return on Assets
FASB		Financial Accounting Standards Board
FERC		Federal Energy Regulatory Commission
FTCFRCC		Federal Trade CommissionFlorida Reliability Coordinating Council
GAAP		Generally Accepted Accounting Principles in the United States
GHG		Greenhouse Gas
GRT		Gross Receipts Tax
GSA		Generation Supply Adjustment
GWh		Gigawatt hour
HAP		Hazardous air pollutants
Health Care Reform Acts		Patient Protection and Affordable Care Act and Health Care and Education Reconciliation Act of 2010
IBEW		International Brotherhood of Electrical Workers
ICC		Illinois Commerce Commission
ICE		Intercontinental Exchange
IFRS		International Financial Reporting Standards
Illinois Act		Illinois Electric Service Customer Choice and Rate Relief Law of 1997
Illinois EPA		Illinois Environmental Protection Agency
Illinois Settlement Legislation		Legislation enacted in 2007 affecting electric utilities in Illinois
IPA		Illinois Power Agency
IRC		Internal Revenue Code
IRS		Internal Revenue Service
ISO		Independent System Operator
ISO-NE		ISO New England Inc.
kV		Kilovolt
kW		Kilowatt
kWh		Kilowatt-hour
LIBOR		London Interbank Offered Rate
LILO		Lease-In, Lease-Out
LLRW		Low-Level Radioactive Waste
LTIP		Long-Term Incentive Plan
MATS		U.S. EPA Mercury and Air Toxics Rule
MDPSC		Maryland Public Service Commission
MGP		Manufactured Gas Plant
MISO		Midwest Independent Transmission System Operator, Inc.
mmcf		Million Cubic Feet
Moody’s		Moody’s Investor Service
MRV		Market-Related Value
MW		Megawatt
MWh		Megawatt hour
n.m.		not meaningful
NAAQS		National Ambient Air Quality Standards
NAV		Net Asset Value
NDT		Nuclear Decommissioning Trust
NEIL		Nuclear Electric Insurance Limited
NERC		North American Electric Reliability Corporation
NJDEP		New Jersey Department of Environmental Protection
Non-RegulatedNon-Regulatory Agreements Units		Former AmerGen nuclearNuclear generating units andor portions of the Peach Bottom nuclear generating unitsthereof whose decommissioning-related activities are not subject to contractual elimination under regulatory accounting
NOV		Notice of Violation

GLOSSARY OF TERMS AND ABBREVIATIONS
Exelon Corporation and Related Entities
Other Terms and Abbreviations
NPDES		National Pollutant Discharge Elimination System
NRC		Nuclear Regulatory Commission
NWPA		Nuclear Waste Policy Act of 1982

GLOSSARY OF TERMS AND ABBREVIATIONS
Exelon Corporation and Related Entities
Other Terms and Abbreviations
NYMEX		New York Mercantile Exchange
OCI		Other Comprehensive Income
OIESO		Ontario Independent Electricity System Operator
OPEB		Other Postretirement Employee Benefits
PA DEP		Pennsylvania Department of Environmental Protection
PAPUC		Pennsylvania Public Utility Commission
PCCA		Pennsylvania Climate Change Act
PGC		Purchased Gas Cost Clause
PJM		PJM Interconnection, LLC
POLR		Provider of Last Resort
POR	��	Purchase of Receivables
PPA		Power Purchase Agreement
Prescription DrugPrice-Anderson Act		Medicare Prescription Drug Improvement and Modernization DrugPrice-Anderson Nuclear Industries Indemnity Act of 20031957
PRP		Potentially Responsible Parties
PSEG		Public Service Enterprise Group Incorporated
PUHCAPV		Public Utility Holding Company Act of 1935
PURTA		Pennsylvania Public Realty Tax ActPhotovoltaic
RCRA		Federal Resource Conservation and Recovery Act of 1976, as amended
REC		Renewable Energy Credit which is issued for each megawatt hour of generation from a qualified renewable energy source
Regulatory Agreement Units		Former ComEd and former PECO nuclearNuclear generating units whose decommissioning-related activities are subject to contractual elimination under regulatory accounting
RES		Retail Electric Suppliers
RFP		Request for Proposal
RGGI		Regional Greenhouse Gas Initiative
Rider		Reconcilable Surcharge Recovery Mechanism
RMC		Risk Management Committee
RPM		PJM Reliability Pricing Model
RPS		Renewable Energy Portfolio Standards
RPM		PJM Reliability Pricing Model
RTEP		Regional Transmission Expansion Plan
RTO		Regional Transmission Organization
S&P		Standard & Poor’s Ratings Services
SEC		United States Securities and Exchange Commission
SECASERC		Seams Elimination Charge/Cost Adjustments/AssignmentSERC Reliability Corporation (Formerly Southeast Electric Reliability Council)
SERP		Supplemental Employee Retirement Plan
SFC		Supplier Forward Contract
SGIG		Smart Grid Investment Grant
SILO		Sale-In, Lease-Out
SMP		Smart Meter Program
SNF		Spent Nuclear Fuel
SOS		Standard Offer Service
SPP		Southwest Power Pool
SSCM		Simplified Service Cost Method
Tax Relief Act of 2010		Tax Relief, Unemployment Insurance Reauthorization and Job Creation Act of 2010
TEG		Termoelectrica del Golfo
TEP		Termoelectrica Penoles
Upstream		Natural gas exploration and production activities
VIE		Variable Interest Entity
WECC		Western Electric Coordinating Council

FILING FORMAT

This combined Form 10-Q is being filed separately by the Registrants. Information contained herein relating to any individual registrant is filed by such registrant on its own behalf. No registrant makes any representation as to information relating to any other registrant.

FORWARD-LOOKING STATEMENTS

Certain of the matters discussed in this Report are forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, that are subject to risks and uncertainties. The factors that could cause actual results to differ materially from the forward-looking statements made by a Registrant include (a) those factors discussed in the following sections of the Registrants’ 2010Exelon’s 2011 Annual Report on Form 10-K: ITEM 1A. Risk Factors, as updated by Part II, ITEM 1A of this Report; ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations, as updated by Part I, ITEM 2. of this Report; and ITEM 8. Financial Statements and Supplementary Data: Note 18, as updated by Part I, Item 1. Financial Statements, Note 1315 of this Report; (b) those factors discussed in the following sections of the Constellation Energy Group, Inc.’s 2011 Annual Report on Form 10-K: ITEM 1A. Risk Factors, as updated by Part II, ITEM 1A of this Report; ITEM 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations, as updated by Part I, ITEM 2. of this Report; and (b)ITEM 8. Financial Statements and Supplementary Data: Note 12, as updated by Part I, ITEM 1. Financial Statements, Note 15 of this Report; and (c) other factors discussed herein and in other filings with the SEC by the Registrants. Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this Report. None of the Registrants undertakes any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this Report.

WHERE TO FIND MORE INFORMATION

The public may read and copy any reports or other information that the Registrants file with the SEC at the SEC’s public reference room at 100 F Street, N.E., Washington, D.C. 20549. The public may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330. These documents are also available to the public from commercial document retrieval services, the website maintained by the SEC atwww.sec.gov and the Registrants’ websites atwww.exeloncorp.com. Information contained on the Registrants’ websites shall not be deemed incorporated into, or to be a part of, this Report.

PART I. FINANCIAL INFORMATION

Item 1.    Financial Statements

EXELON CORPORATION

EXELON CORPORATION AND SUBSIDIARY COMPANIES

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME

(Unaudited)

See the Combined Notes to Consolidated Financial Statements

EXELON CORPORATION AND SUBSIDIARY COMPANIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

See the Combined Notes to Consolidated Financial Statements

EXELON CORPORATION AND SUBSIDIARY COMPANIES

CONSOLIDATED BALANCE SHEETS

(Unaudited)

See the Combined Notes to Consolidated Financial Statements

EXELON CORPORATION AND SUBSIDIARY COMPANIES

CONSOLIDATED BALANCE SHEETS

(Unaudited)

See the Combined Notes to Consolidated Financial Statements

EXELON CORPORATION AND SUBSIDIARY COMPANIES

CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS’ EQUITY

(Unaudited)

See the Combined Notes to Consolidated Financial Statements

EXELON GENERATION COMPANY, LLC

EXELON GENERATION COMPANY, LLC AND SUBSIDIARY COMPANIES

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME

(Unaudited)