On the 18th anniversary of the assassination of the Rev. Martin Luther King Jr., a coalition of religious, peace, student, labor and other groups picketed outside the WWDC-FM studios yesterday, objecting to the continued employment of disc jockey Doug (Greaseman) Tracht.

Two months ago on the holiday celebrating King's birthday, Tracht said on the air that if the killing of one black leader was cause for a day off, then killing "four more" should result in getting the rest of the week off. Although Tracht immediately apologized, the station has been picketed several times and some advertisers have pulled their commercials from his enormously popular morning show on DC-101.

Yesterday's action, which started with a rally in Lafayette Park and was followed by a short walk to the radio station, at 1150 Connecticut Ave. NW, was organized by the recently created Campaign Against Broadcasting Bigotry. About 25 people formed a line outside the studio, shouting, "Release the Grease" and "Greaseman's gotta go."

"We're fired up, we won't take it no more!" shouted the Rev. Henry A. Silva, the campaign coordinator. Speaking of the legacy of "good will" that King left America, he said, "On Jan. 20 all this good will was shattered . . . by one man's comments that defied and angered blacks and whites." As for Tracht's apologies, Silva said, "As a Christian I understand the beauty of an apology. But if you step on my foot and apologize, my foot still hurts. We are hurting."

Silva, regional director of the Southern Christian Leadership Conference, said he went to the offices of WWDC yesterday morning to ask for an appointment with management but was escorted out by a security guard. At the afternoon picketing, Silva, Helen Tate, local coordinator for the King Center for Nonviolent Social Change, and Louise Franklin-Ramirez, a representative of the Gray Panthers, attempted to go up to the station's offices but were turned away by a guard. Silva said he planned to file a suit next week protesting the station's barring of his group.

The sentiment against Tracht and the station, said Silva, "continues to escalate, and we are going to come back once a week." Many of the speakers at Lafayette Park linked public tolerance of Tracht's remarks to the conservative mood of the country. "Reaganism, Ramboism and racism are of a piece," said David Hostetter, coordinator of the Washington Peace Center. "It is no accident that Ramboism coincides with Greaseman's racism."

* During the picketing, one woman in a car on Connecticut Avenue rolled down her window and shouted, "Have a sense of humor." The station had no comment on yesterday's picketing or Silva's statement, according to a spokesman.