Senate leaders were awaiting word from the White House yesterday on a plan that would keep the Civil Rights Commission from going out of business at midnight tonight as well as keep in office three Democratic members President Reagan wants to oust.

The White House, sources said, was still searching for a way to get rid of at least one of the Democrats, Mary F. Berry, assistant secretary of education in the Carter administration and perhaps the commission's most outspoken member.

The current authorization bill for the 26-year-old commission expires at midnight tonight with the end of the current fiscal year. A new authorization bill for the six-member panel has been held up for months by the controversy over Reagan's announcement last May that he was nominating three new commissioners to replace Berry, Blandina Cardenas Ramirez and Rabbi Murray Saltzman.

Reagan critics threatened to block the nominations and Reagan supporters threatened in turn to let the commission die. The nominations would give Reagan control of the commission, which has been a sharp thorn in his side, repeatedly criticizing his stances on affirmative action, quotas and a wide range of other civil rights issues.

The commissioners serve open-ended terms, and civil rights groups have argued that nothing in the law "expressly authorizes the president" to dismiss any. Berry and Ramirez, a San Antonio educator, were appointed by President Carter. Saltzman was named by President Ford.

Sources said that under the compromise broached yesterday to presidential counselor Edwin Meese III, the commission would be expanded to eight members.

All six of the current members would be reappointed, two to two-year terms, two to four and two to six, and Reagan would be able to make two more appointments immediately. The new commissioners, sources said, would be given eight-year terms. Then, if Reagan is reelected, he would have the chance to replace the two most senior members in 1985, and two more in 1987, in each case with eight-year appointees.

"What it really means," one source said, "is that up to the 1984 election, there would still be a goodly number of people on the commission who are not Reagan appointees. If he wins in '84, he gets some more . . . . But the commission would remain strictly bipartisan, with no more than four from any one party. The best thing is that no more than four Civil Rights Commission terms could expire in a single presidential term. And no one could be fired except for cause."

Meese, it was learned, was asked yesterday whether the White House would accept the plan, but he left at midday for a trip to California without sending word. Reagan has nominated three new appointees, New York civil rights lawyer Morris Abrams, educator John H. Bunzel, and law professor Albert A. Destrow. The compromise would require one to withdraw.

"It's in Ed Meese's court now," one congressional source said last evening. "The markup on the authorization bill is scheduled for tomorrow Friday ."

"We've got everybody on board but the White House," another source said. "All the civil rights organizations have signed on."

The Senate Judiciary Committee was scheduled to take up the issue yesterday, but then postponed the session until this morning in light of the uncertainties. Although the commission is technically supposed to expire tonight, the agency would have a 60- or 90-day wind-down period during which it could be revived.