Oil Industry Merger Antitrust Enforcement Act - Amends the Clayton Act to require, in any civil action in which the plaintiff alleges that the effect of a merger, acquisition, or other transaction (transaction) may be to substantially lessen competition or to create a monopoly in the business of exploring for, producing, refining, marketing, or selling petroleum, oil, natural gas, or their related products and that establishes that the transaction involves competitors in that business, the burden of proof shall be on the defendant to establish that such transaction will not substantially lessen competition or create a monopoly.

Directs the Federal Trade Commission (FTC) and the Antitrust Division of the Department of Justice to jointly review and revise applicable enforcement guidelines and policies in order to: (1) specifically address the above transactions; and (2) ensure that the guidelines will prevent any transaction which substantially lessens competition or creates a monopoly.