For the last four years, the Legal Services Corp. has played a major role in an ideological drama, the very symbol of liberal activism struggling for survival in a hostile world of Reagan-style conservatism.

But if the size of the part was bigger than usual, the plot had a familiar ring.

Since 1974, when Congress established the federally funded but legally independent agency to provide legal help for the poor, Legal Services has made repeated cameo appearances on the political stage, usually being reviled by conservatives as a haven for trouble-makers and malcontents or lionized by liberals as a beacon of social justice for the oppressed.

The dialogue got sharper and the limelight brighter under President Reagan, who vowed to abolish the corporation and has since failed to win Senate approval for any of the 18 persons he has nominated to its 11-member board.

The board's membership became the focus of the Legal Services debate during Reagan's first term, with Democrats (and some Republicans) loudly complaining that the White House intended to stack it with persons antagonistic to the entire concept of legal services.

If Reagan started that war, however, he did it 10 years ago.

The practice of rejecting or blocking Legal Services directors has a relatively short but consistent history in the Senate, and the first nominee to get the cold shoulder was appointed by President Gerald R. Ford in 1974 at the suggestion of Gov. Ronald Reagan.

The nominee was William Knecht, a California Farm Bureau Federation lawyer who had led a campaign to discredit legal-aid lawyers representing the state's farm workers. The Senate Labor and Public Welfare Committee eventually blocked Knecht's nomination because of a "strong likelihood that he would serve to obstruct" the agency's work.

Two other Ford nominees to the fledgling corporation's first board withdrew in the face of criticism that they lacked sufficient commitment to the poor.

President Jimmy Carter had little better luck with his last batch of nominees, who were blocked by Senate Republicans and disappeared into the ethers of history when Carter left office.

Both Ford and Carter were able to have boards confirmed at one time or another, however. During the Reagan administration, the corporation has been operated piecemeal by several rounds of recess appointees, the latest commissioned last November.

By using his constitutional power to appoint officials while Congress is out of session, Reagan has succeeded in installing board members who almost certainly would have been blocked by the Senate -- including an attorney who once called a Hispanic judge a "professional Mexican."

Not surprisingly, Reagan also has succeeded in provoking Legal Services' congressional allies, who have retaliated by making it unlawful for the corporation to cut off any grant recipients until the Senate has confirmed a board.

The restriction hasn't stopped the interim board members from making several controversial administrative changes, however, including stringent rules that bar its grantees from almost any lobbying or grass-roots organizing.

Republican partisans were hopeful this week that the recently announced resignation of the corporation's controversial president, Donald P. Bogard, will signal smoother days for the agency.

Bogard, hired two years ago by a recess-appointed board, was heatedly opposed by legal-aid advocates, largely because of his previous job. He was a lawyer for Stokley-Van Camp Inc., where he was involved in fighting suits brought by Legal Services lawyers on behalf of migrant farm workers.

"We are hoping the tenor has changed," said a staff aide on the Senate Labor and Human Resources Committee. He said the committee intended to move "as quickly as we can" in confirming Reagan's latest batch of formal nominees, whose names were delivered to the committee Jan. 3.

But at Legal Services, nobody is holding his breath.

"There really is no consensus in the Congress on what Legal Services should be," said corporation official Jim Streeter. "There are strongly held but opposing ideas, and it's always easier to defeat something than to carry it out."