UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. 4)*

GenOn Energy, Inc.

(Name of Issuer)

Common Stock, par value $0.001 per share

(Title of Class of Securities)

37244E107

(CUSIP Number)

December 31, 2011

(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)

* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see Instructions).

CUSIP No.: 37244E107
1 NAME OF REPORTING PERSON
Orbis Investment Management Limited ("OIML")

I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)
2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
(a)  [   ]
(b)  [   ]
3 SEC USE ONLY
 
4 CITIZENSHIP OR PLACE OF ORGANIZATION
The Reporting Person is a company organized under the laws of Bermuda
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH 5 SOLE VOTING POWER
67,341,857
6 SHARED VOTING POWER
0
7 SOLE DISPOSITIVE POWER
67,341,857
8 SHARED DISPOSITIVE POWER
0
9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
67,341,857
10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES []

11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
12 TYPE OF REPORTING PERSON
FI (OIML)

CUSIP No.: 37244E107
ITEM 1(a). NAME OF ISSUER:
GenOn Energy, Inc.
ITEM 1(b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:
1000 Main Street, Houston, Texas 77002 USA
ITEM 2(a). NAME OF PERSON FILING:
Orbis Investment Management Limited ("OIML")
ITEM 2(b). ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:
Orbis House, 25 Front Street, Hamilton Bermuda HM11
ITEM 2(c). CITIZENSHIP:
The Reporting Person is a company organized under the laws of Bermuda.
ITEM 2(d). TITLE OF CLASS OF SECURITIES:
Common Stock, par value $0.001 per share
ITEM 2(e). CUSIP NUMBER:
37244E107
ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO SECTION 240.13d-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 Act (15 U.S.C. 78c);
(b) [   ]  Bank as defined in Section 3(a)(6) of the Act (15 U.S.C. 78c);
(c) [   ]  Insurance company as defined in Section 3(a)(19) of the Act (15 U.S.C. 78c);
(d) [   ]  Investment company registered under Section 8 of the Investment Company Act of 1940
(15 U.S.C 80a-8);
(e) [   ]  An investment adviser in accordance with 240.13d-1(b)(1)(ii)(E);
(f) [   ]  An employee benefit plan or endowment fund in accordance with 240.13d-1(b)(1)(ii)(F);
(g) [   ]  A parent holding company or control person in accordance with 240.13d-1(b)(1)(ii)(G);
(h) [   ]  A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act
(12 U.S.C. 1813);
(i) [   ]  A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j) [X]  A non-U.S. institution in accordance with 240.13d-1(b)(1)(ii)(J);
(k) [   ]  Group, in accordance with 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution
in accordance with 240.13d1(b)(1)(ii)(J), please specify the type of institution:
ITEM 4. OWNERSHIP:
Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.
(a) Amount beneficially owned:
Orbis Investment Management Limited 67,341,857
(b) Percent of class:
8.7%
(c) Number of shares as to which the person has:
(i)   Sole power to vote or to direct the vote:
67,341,857
(ii)  Shared power to vote or to direct the vote:
0
(iii) Sole power to dispose or to direct the disposition of:
67,341,857
(iv) Shared power to dispose or to direct the disposition of:
0
ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS:
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:
Other persons have the right to receive and the power to direct the receipt of dividends from, or the proceeds from the sale of the 67,341,857 shares of common stock of GenOn Energy, Inc. beneficially owned by Orbis Investment Management Limited.  
ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY:
 
ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP:
 
ITEM 9. NOTICE OF DISSOLUTION OF GROUP:
 
ITEM 10. CERTIFICATION:
By signing below I certify that, to the best of my knowledge and belief, the foreign regulatory scheme applicable to Orbis Investment Management Limited is substantially comparable to the regulatory scheme applicable to the functionally equivalent U.S. institution(s). I also undertake to furnish to the Commission staff, upon request, information that would otherwise be disclosed in a Schedule 13D.

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 14, 2012
Date
Orbis Investment Management Limited
/s/ James J. Dorr
Signature
James J. Dorr, General Counsel
Name/Title



Attention: Intentional misstatements or omissions of fact constitute Federal criminal violations (see 18 U.S.C. 1001).