With the gallantry of a river-boat gambler whose bluff has just been called, Rep. Jack Brooks (D-Tex.) yesterday folded his cards and conceded President Carter a handsome victory in their battle over government reorganization procedures.

Brooks, who once said the Carter plan "stands the Constitution on its head," pushed his House Government Operations subcommittee into quick and unanimous approval of a slightly modified version of the original Carter proposal.

Yesterday morning's action took only a half-hour, and equal dispatch is expected Thursday when the full Government Operations Committee meets to clear the reorganization authority bill. House floor action is planned for next week.

Under the proposal approved yesterday, Carter preserves his principal objective -- having reorganization plans take effect automatically unless vetoed by the House or Senate within 60 days.

It was the one-house veto provision that Brooks called unconstitutional and that he vowed to oppose.

But after Carter lined up a near-majority of the committee for his bill and two days of hearings produced no wavering of that support, "It was time to take a look at what the cards were," Brooks said yesterday.

"The President was just determined to stay with his proposal," Brooks said, "and he's got the votes probably to do it."

Members of Brooks' committee, who wanted to avoid a test of strength between the chairman and the President, took the initiative in working out a compromise that saved some of Brooks' objectives, without severely restricting Carter.

That compromise was offered yesterday by Rep. William S. Moorhead (D-Pa.). It picked up from Brooks' proposal a provision that makes it easier to obtain a floor vote in the House and Senate on each reorganization plan.

It provides that each time the President sends a reorganization plan to Congress, Brooks and his Senate counterpart, Sen. Abraham A. Ribicoff (D-Conn.), would immediately file a pro forma resolution of disapproval. The Senate and House Government Operations committees would be discharged of their jurisdiction over the reorganization plan after 45 days, leaving 15 days in which any member of the House or Senate could call up the resolution of disapproval for a vote.

That is a step short of Brooks' original goal of requiring an affirmative vote of approval by both house and Senate on each reorganization plan, but he said it "increases the orle of Congress in the process" beyond the original Carter proposal.

Another feature of the compromise is that Carter could have no more than three reorganization plans pending at any time, each of them limited to a single subject-matter. Carter's original bill contained no limit on subject-matter or the number or plans.

Like the bill already passed by the Senate, the compromise bars the President from eliminating Cabinet-level departments, or independent regulatory agencies by a reorganization plan. It allows him to amend his own plan within 30 days of submission.

Brooks himself took on the role of speeding the compromise through the subcommittee, brushing aside a move to reduce the number of plans pending at a time from three to two, and supporting an extension of the authority from two years to three.

White House press secretary Jody Powell said Carter was "very pleased" by the subcommittee action, particularly that "the early disagreements within that committee were resolved in a way that permitted a unanimous vote of approval."