After a luncheon of beef stroganoff over rice yesterday at the Capitol Hill Club, bastion of establishment Republicanism, National Chairman Richard Richards proudly introduced to an assemblage of television cameras and microphones a dozen black ministers from Prince George's County who recently converted to the GOP.

"This may be one of the most significant things that has happened to the Republican party in many, many years," said Richards. "We have been trying for a long time to make inroads into the black community," he said at a press conference at RNC headquarters which also attracted Lawrence J. Hogan, the Prince George's County executive and a GOP candidate for the Senate.

The ministers switched party registrations en masse two weeks ago, announcing a goal of bringing 10,000 new black Republicans with them.

One of the new Republicans, the Rev. Perry Smith of the First Baptist Church of North Brentwood, is an undeclared candidate for Congress in the 5th Congressional District, against incumbent Democrat Rep. Steny Hoyer. About 40 percent of the district's population is nonwhite.

"Our reasons for switching are to obtain meaningful access to the political process in Prince George's County," said the Rev. William Smith of the Jordan Baptist Church in Capitol Heights, as Richards beamed with approval. "This is the only way to end the dominance of the Democratic machine," Smith went on.

Democrat State Sen. Tommie Broadwater, the top elected black official in Prince George's County, dismissed Perry Smith's conversion.

"I've known Perry Smith for a long time," Broadwater said, when contacted in Annapolis. "I know he's had as much access as anybody else. He's running as a Republican because he knows that in a Democratic primary he couldn't beat Steny Hoyer."

The new black Republicans, stressing that their aims and interests are in local politics, declined to comment on the impact of President Reagan's social and economic policies on the black community.

"On the level at which we are involved we are certainly concerned (but) I can't make any national comments," said Smith.

Smith insisted that as Republicans he and his fellow ministers will be "critical and analytical" voices within the party and that his move "does not suggest a blanket or blind endorsement of anything."

Richards said the national party has made firm commitments of financial backing to at least four black Republican congressional candidates "to the maximum extent that the law allows us to do."

Although Richards would not say if Perry Smith would get such support, another party official indicated Smith would get the backing if he is the only Republican to seek the nomination.

Richards said funding of black candidates will begin with $56,300 from the RNC and Republican National Congressional Committee. "Obviously we are going to direct PAC money as well," he added.