The Prince George's County Bar Association, which excluded women from membership until about 12 years ago, has given its highest vote to fill a vacant District Court judgeship to a woman, virtually assuring that she will become the first woman to hold a full-fledged judgeship in Prince George's.

Audrey Melbourne, 46, a Laurel lawyer who had unsuccessfully sought judgeships three times, is also said to have the requisite political backing to ultimately obtain the gubernatorial appointment over three male competitors. In the bar voting , she defeated her closest opponent, Gradon S. (Skip) McKee III by a single vote, 190 to 189.

In the critical bar association race, Melbourne was given a clear field by other women who have previously competed for judgeships. "I think we all didn't want to cloud it all up again," said Stewart Oneglia, a parttime probate jurist who was one of the woman competitors.

"I indicated to a number of women who asked me." said State Senate President and Prince George's political power Steny Hoyer, "that I felt it important a woman be appointed but if they split the vote it would be difficult . . . "

Hoyer said he also "indicated I intended to vote for Mrs. Melbourne, and that in my judgement, Mrs. Melbourne would do best" in the bar voting.

The District of Columbia bench contains five women, three on the trial court, two at the appellate level. In Northern Virginia, there is a female juvenile judge in Alexandria. Montgomery County has had one woman Circuit Court hudge, now retired.

Technically, judicial appointments in Maryland are made by the governor, from a list of "legally and professionally most fully qualified" candidates submitted to him by nomination commissions in each circuit.

In practice, the bar association votes and political endorsements weigh most heavily. In only one instance has the biweekly "Breakfast Club" of elected county Democrats failed to back th e winner of the bar poll. In that case, Sylvania Woods, a black attorney, was chosen to fill what was unofficially designated a "black" District Court seat.

The judicial nominating commission for the Seventh Circuit - Prince George's, Calvert, Charles and St. Mary's counties - is scheduled to meet Feb. 1 on two Prince George's District Court vacancies.

To achieve the "most fully qualified" rating, a candidate must receive seven votes of a possible 13. In the last judgeship race, with two Prince George's seats unfilled and other commissioners absent, political favorite received only five votes, and, therefore, could not get the slot.

Since then, one of the Prince George's commission vacancies has been filled, and Melbourne's approval is considered a virtual certainty.

Melbourne is widely respected in the county's legal community. She has practiced law since 1962, is president of the Iron Bridge Hunt Club, and is married to a real estate broker who once was mayor of Laurel.

The reason there has never been a woman judge in the county, she said in an interview, is that few female lawyers have practiced there until recently. By one estimate, there now are about 35 women practicing law in Prince George's.

The bar results on the second District Court vacancy are not yet in, but the political frontrunner is said to be Del. John Wolfgang, (D-Prince George's) of Tantallon, brother-in-law of Maryland Secretary of State Fred L. Wineland.

Wolfgang said in an interview that he has solicited and received the support of both Steny Hoyer, President of the State Senate, and Peter F. O'Malley, a Prince George's County attorney who is a behind-the-scenes political power.

Although six other candidates are competing with Wolfgang, bar observers say none has an especially large following. Nonetheless, the Wolfgang judgeship is tinged with controversy.

Because of his political support, several lawyers say, formidable challengers have been discouraged from running. There also is a school of though that the judgeship is a way to retire Wolfgang gracefully from his General Assembly Economic Matters Committee chairmanship. Then there is the health issue.

Wolfgang obtained the chairmanship last year when Del. Martin Becker, who held it previously, became a Montgomery County Circuit Judge. According to state and county sources, Wolfgang - who suffered a heart attack in 1974 - expressed concern at the time that his health might preclude carrying out the chairman's duties.

Hoyer said that Wolfgang, at the time, concluded that "he was well enough to handle those responsibilities, and in fact he has been . . ."

Wolfgang said becoming a judge is his own idea. "Circuit Court is the ultimate for me. District Court is the training ground," he said. He said he expected the health issue to be raised by critics. "I'll run you around the block every day of the week," he said, describing his health as "excellent."

Nonetheless, some members of the judicial nominating commission reportedly are concerned about the issue. For the first time since its creation in 1970, the commission plans to personally interview candidates at its next meeting.

"Health is a legitimate question," chairman John A. Buchanan said yesterday. "The last time I saw John, he looked fine. I hope he is. I hope everybody is."