CORPORATE OFFICE PROPERTIES TR, INC.

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13G/A

(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO RULES 13d-1(b), (c), AND (d) AND AMENDMENTS THERETO FILED

PURSUANT TO RULE 13d-2(b)

( AMENDMENT 3)

CORPORATE OFFICE PROPERTIES TRUST

( NAME OF ISSUER )

COMMON STOCK

(Title of Class of Securities)

22002T108

(CUSIP Number)

DECEMBER 29, 2006

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

X Rule 13d-1 (b)

Rule 13d-1 (c)

Rule 13d-1 (d)

CUSIP No. 22002T108

13G/A

Page 1 of 3 pages

1.	Names of reporting persons	Security Capital Research & Management Incorporated
	I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)		36-4130398

2.	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*	(a)
		(b)

3.	SEC USE ONLY

4.	CITIZENSHIP OR PLACE OF ORGANIZATION
	Delaware

NUMBER OF	5.	SOLE VOTING POWER	1,944,529
SHARES
BENEFICIALLY	6.	SHARED VOTING POWER	0
OWNED BY
EACH	7.	SOLE DISPOSITIVE POWER	2,664,603
REPORTING
PERSON WITH	8.	SHARED DISPOSITIVE POWER	0

9.	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,664,603

10.	CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
	CERTAIN SHARES

11.	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	6.2%

12.

TYPE OF REPORTING PERSON*

Item 1(a).	Name of Issuer:
	CORPORATE OFFICE PROPERTIES TRUST

Item 1(b).	Address of Issuer's Principal Executive Offices:
	8815 CENTER PARK DRIVE SUITE 400 COLUMBIA, MD 21045

Item 2(a).	Name of Person Filing:
	Security Capital Research & Management Incorporated

Item 2(b).	Address of Principal Business Office or, if None, Residence:
	10 South Dearborn Street, Suite 1400
	Chicago, Illinois 60603

Item 2(c).	Citizenship
	Delaware

Item 2(d).	Title of Class of Securities:
	COMMON STOCK
	Unless otherwise noted, security being reported is common stock

Item 2(e).

CUSIP Number:

22002T108

Item 3	If this Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b)
	Or (c), Check Whether the Person Filing is a :

(a)		Broker or dealer registered under Section 15 of the Exchange Act;
(b)		Bank as defined in Section 3(a)(6) of the Exchange Act;
(c)		Insurance company as defined in Section 3(a)(19) of the
		Exchange Act;
(d)		Investment company registered under Section 8 of the Investment
		Company Act;
(e)	X	An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);
(f)		An employee benefit plan or endowment fund in accordance with
		Rule 13d-1(b)(1)(ii)(F);
(g)		A parent holding company or control person in accordance with
		Rule 13d-1(b)(1)(ii)(G);
(h)		A savings association as defined in Section 3(b) of the Federal
		Deposit Insurance Act;
(i)		A church plan that is excluded from the definition of an
		Investment company under Section 3(c)(14) of the Investment
		Company act;
(j)		Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to Rule 13d-1(b), check this box.

Page 2 of 3 pages

Item 4. Ownership

Provide the following information regarding the aggregate number and

Percentage of the class of securities of issuer identified in Item 1.

(a) Amount beneficially owned: 2,664,603

Including 0 shares where there is a Right to Acquire.

(b) Percent of class: 6.2%

(c) Number of shares as to which such person has:

(i) Sole power to vote or to direct the vote: 1,944,523

(ii) Shared power to vote or to direct the vote: 0

(iii) Sole power to dispose or to direct the disposition of: 2,664,603

(iv) Shared power to dispose or to direct the disposition of: 0

Item 5. Ownership of Five Percent or Less of a Class. NOT APPLICABLE

If this statement is being filed to report the fact that as of the date

hereof the reporting person has ceased to be the beneficial owner of more

than five percent of the class of securities, check the following. ( )

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

Security Capital Research & Management Incorporated is the beneficial owner of 2,664,603 shares of the

issuer's common stock on behalf of other persons known to have one or more of

the following:

the right to receive dividends for such securities;

the power to direct the receipt of dividends from such securities;

the right to receive the proceeds from the sale of such securities;

the right to direct the receipt of proceeds from the sale of such securities;

No such person is known to have an interest in more than 5% of the class of

securities reported herein unless such person is identified below.

Item 7. Identification and Classification of the Subsidiary Which Acquired the

Security being reported on by the Parent Holding Company.

Not Applicable

Item 8. Identification and Classification of Members of the Group.

Not Applicable

Item 9. Notice of Dissolution of Group.

Not Applicable

Item 10. Certifications

By signing below I certify that, to the best of my knowledge and belief,

the securities referred to above were not acquired and are not held for the

purpose of or with the effect of changing or influencing the control of the

issuer of the securities and were not acquired and are not held in connection

with or as a participant in any transaction having that purpose or effect.

Page 3 of 3 pages

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the

information set forth in this statement is true, complete and correct.

Dated: FEBRUARY 15,2007	Security Capital Research & Management Incorporated
	By: /s/ Michael J. Heller
	--------------------------------------
	Michael J. Heller
	Vice President and Controller

The original statement shall be signed by each person on whose behalf the statement

is filed or his authorized representative. If the statement is signed on behalf of

a person by his authorized representative (other than an executive officer or general

partner of the filing person), evidence of the representative's authority to sign on

behalf of such person shall be filed with the statement, provided, however, that a

power of attorney for this purpose which is already on file with the commission may

be incorporated by reference. The name and any title of each person who signs the

the statement shall be typed or printed beneath his signature.

Provide the following information regarding the aggregate number and
Percentage of the class of securities of issuer identified in Item 1.
	(a)	Amount beneficially owned: 2,664,603
		Including 0 shares where there is a Right to Acquire.
	(b)	Percent of class: 6.2%
	(c)	Number of shares as to which such person has:
			(i)	Sole power to vote or to direct the vote:	1,944,523
			(ii)	Shared power to vote or to direct the vote:	0
			(iii)	Sole power to dispose or to direct the disposition of:	2,664,603
			(iv)	Shared power to dispose or to direct the disposition of:	0


Security Capital Research & Management Incorporated is the beneficial owner of 2,664,603 shares of the
issuer's common stock on behalf of other persons known to have one or more of
the following:
	the right to receive dividends for such securities;
	the power to direct the receipt of dividends from such securities;
	the right to receive the proceeds from the sale of such securities;
	the right to direct the receipt of proceeds from the sale of such securities;
No such person is known to have an interest in more than 5% of the class of
securities reported herein unless such person is identified below.

Item 7.	Identification and Classification of the Subsidiary Which Acquired the
	Security being reported on by the Parent Holding Company.
Not Applicable

Item 8.	Identification and Classification of Members of the Group.
	Not Applicable

Item 9.	Notice of Dissolution of Group.
	Not Applicable