UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 CORPORATE OFFICE PROPERTIES TRUST - -------------------------------------------------------------------------------- (NAME OF ISSUER) COMMON SHARES - -------------------------------------------------------------------------------- (TITLE OF CLASS OF SECURITIES) 22002T108 - -------------------------------------------------------------------------------- (CUSIP NUMBER) DECEMBER 31, 2004 - -------------------------------------------------------------------------------- (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [_] Rule 13d-1(b) [X] Rule 13d-1(c) [_] Rule 13d-1(d) CUSIP NO. 22002T108 13G PAGE 2 OF 6 PAGES - -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS ING Groep N.V. - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) [_] Not Applicable (b) [_] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION The Netherlands - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER 1,963,200(1) NUMBER OF --------------------------------------------------------- SHARES 6 SHARED VOTING POWER BENEFICIALLY OWNED BY EACH 0 REPORTING --------------------------------------------------------- PERSON WITH: 7 SOLE DISPOSITIVE POWER 1,963,200(1) --------------------------------------------------------- 8 SHARED DISPOSITIVE POWER 0 - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,963,200 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES [_] Not Applicable - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 5.3%(2) - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON HC - -------------------------------------------------------------------------------- - ---------- 1 These shares are held by indirect subsidiaries of ING Groep N.V. in their role as a discretionary manager of client portfolios. 2 As of November 2, 2004, 36,801,533 common shares were issued and outstanding. Source: Issuer's Form 10-Q for the quarter ended September 30, 2004. -2- ITEM 1(A). NAME OF ISSUER: Corporate Office Properties Trust ITEM 1(B). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES: 8815 Centre Park Drive Suite 400 Columbia, MD 21045 ITEM 2(A). NAME OF PERSON FILING: ING Groep N.V. ITEM 2(B). ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE: Amstelveenseweg 500 1081 KL Amsterdam P.O. Box 810 1000 AV Amsterdam The Netherlands ITEM 2(C). CITIZENSHIP: See item 4 on Page 2 ITEM 2(D). TITLE OF CLASS OF SECURITIES: Common Shares ITEM 2(E). CUSIP NUMBER: 22002T108 ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO RULES 13D-1(B), OR 13D-2(B) OR (C), CHECK WHETHER THE PERSON FILING IS A: (Not Applicable) (a) |_| Broker or dealer registered under Section 15 of the Securities Exchange Act of 1934, as amended (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; -3- (d) |_| Investment company registered under Section 8 of the Investment Company Act of 1940, as amended (the "Investment Company Act"); (e) |_| Investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E) under the Exchange Act; (f) |_| Employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F) under the Exchange Act; (g) |_| Parent holding company or control person in accordance with Rule 13d-1(b)(ii)(G) under the Exchange Act; (h) |_| Savings association as defined in Section 3(b) of the Federal Deposit Insurance Act; (i) |_| 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) under the Exchange Act. ITEM 4. OWNERSHIP. (a) Amount beneficially owned: See item 9 on Page 2 (b) Percent of class: See item 11 on Page 2 (c) Number of shares as to which such person has: (i) Sole power to vote or to direct the vote: See item 5 on Page 2 (ii) Shared power to vote or to direct the vote: See item 6 on Page 2 (iii) Sole power to dispose or to direct the disposition of: See item 7 on Page 2 -4- (iv) Shared power to dispose or to direct the disposition of: See item 8 on Page 2 ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS. Not Applicable ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON. Not Applicable ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY OR CONTROL PERSON. 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. CERTIFICATION. By signing below we certify that, to the best of our 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. -5- 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. February 4, 2005 ----------------------------------- (Date) ING GROEP N.V. By: /s/ Cornelis Blokbergen ----------------------------------- (Signature) Cornelis Blokbergen Head Legal Department ----------------------------------- (Name/Title) /s/ Huib D. ter Haar ----------------------------------- (Signature) Huib D. ter Haar Group Compliance Officer ----------------------------------- (Name/Title)