SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
X	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* BARRON HENRY B JR (Last) (First) (Middle) 100 CONSTELLATION WAY (Street) BALTIMORE MD 21202 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol CONSTELLATION ENERGY GROUP INC [ CEG ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director 10% Owner X Officer (give title below) Other (specify below) Executive Vice President
	3. Date of Earliest Transaction (Month/Day/Year) 03/12/2012
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/12/2012		M		7,402(1)	A	$0	30,477.35	D
Common Stock	03/12/2012		F(2)		3,343	D	$35.86	27,134.35	D
Common Stock	03/12/2012		D		27,134.35	D	(3)	0	D
Common Stock	03/12/2012		D		6,862	D	(4)	0	D
Common Stock	03/12/2012		D		418.7336	D	(3)	0	I	By 401 (k)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock options (right to buy)(5)	$90	03/12/2012		D			23,120	(6)	04/01/2018	Common Stock	23,120	(6)	0	D
Stock options (right to buy)(5)	$19.76	03/12/2012		D			103,670	(7)	02/27/2019	Common Stock	103,670	(7)	0	D
Restricted stock units	(8)	03/12/2012		D			7,402	(8)	(8)	Common Stock	7,402	(8)	0	D

Explanation of Responses:

1. This transaction involved the vesting of restricted stock units on 3/12/12 in connection with the Merger described below.

2. This amount represents shares withheld to pay taxes due on the restricted stock units that vested on 3/12/12 and is reported in Table II.

3. Disposition of common stock pursuant to Agreement and Plan of Merger (the "Merger") between Exelon Corporation ("Exelon"), Bolt Acquisition Corporation, and Constellation Energy Group, Inc. ("Constellation"), whereby each share of Constellation common stock, without par value, converted into the right to receive 0.9300 shares of Exelon common stock, without par value, having a closing market value of $39.81 per share on the effective date of the Merger and a cash payment being made for any fractional shares.

4. Disposition of stock units pursuant to the Merger, whereby each Constellation stock unit converted into 0.9300 Exelon stock units with a sale restriction that will lapse on 12/26/12 and a cash payment being made for any fractional shares.

5. These are employee stock options.

6. Pursuant to the Merger, each Constellation stock option vested and converted into an option to purchase 0.9300 shares of Exelon common stock, without par value, at an exercise price of $96.78 per share.

7. Pursuant to the Merger, each Constellation stock option vested and converted into an option to purchase 0.9300 shares of Exelon common stock, without par value, at an exercise price of $21.25 per share.

8. Disposition of restricted stock units pursuant to the Merger. The restricted stock units vested and the shares of Constellation common stock received upon vesting converted into the right to receive 0.9300 shares of Exelon common stock, without par value, having a closing market value of $39.81 per share on the effective date of the Merger and a cash payment being made for any fractional shares. The shares of Constellation common stock received upon vesting are included in the number of shares of Constellation common stock disposed of in the Merger reported in Table I.

	Sean J. Klein, Attorney-In-Fact	03/14/2012
	** Signature of Reporting Person	Date
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