Baltimore Mayor William Donald Schaefer looked distinctly uncomfortable last week when he stood up to address a group of Prince George's County activists -- who have earned a reputation for blocking just the kind of development project the mayor champions in his home town.

"I have a prepared address," he said only half-jokingly. "I have worked hard on it. I am afraid to give it."

Most of those gathered in Oxon Hill for the Prince George's Civic Federation's awards dinner laughed at Schaefer's remark, even though it became clear as he rambled on that he was taking pains to avoid talking about anything controversial.

Schaefer told the crowd that when he walked into the Ramada Inn that evening people began asking him " 'How are you? Are you against growth?'

"I got a feeling," he said. "Something's going on here."

So the mayor, who has been telling people around the state that there is no question that he will run for governor in 1986, embarked on a half-hour discourse about ducks, neighborhoods, the American hostages who were being held in Beirut at the time and Baltimore's Harborplace development.

"I rewrote my speech four times," he said at one point. "I'm going to talk about 'The Star-Spangled Banner.' "

Several people active in county political circles said later that they were surprised that Schaefer -- known throughout the state for his pronounced probusiness, prodevelopment bent -- was invited to speak to a group that has opposed County Executive Parris Glendening's development efforts.

Members of the Prince George's Civic Federation have butted heads with Glendening over plans for the Konterra minicity near Laurel and the Bay of the Americas waterfront project near the Woodrow Wilson Bridge.

They have won partial and in some cases complete victories in their battles against creeping development, notably in their successful attempt to halt Brookefield, another proposed minicity that was to have been built near Brandywine.

Schaefer's presence at the banquet was certainly a ticket-seller. It was in every way another stop on his whistlestop tour around the state as an unofficial gubernatorial candidate; he said that he does not plan to formally announce his intentions until later this year.

In a county where he is regarded fondly by much of elected officialdom, his foray into southern Prince George's last week is likely to be the closest he gets to a genuinely hostile audience, at least until Attorney General Stephen H. Sachs maneuvers a confrontation between himself and the mayor as the contest for the state's top spot heats up.

But if this was the most hostile crowd Schaefer ever has to face in Prince George's County, Sachs and Speaker of the House Benjamin L. Cardin, another Democratic gubernatorial hopeful, have a lot of work to do.

The response to Schaefer's appearance, federation president R. Dan Ritchie said, was "absolutely positive from every corner; very upbeat."

Ritchie said he did not know why the mayor appeared uneasy in front of his group.

"I can only surmise he didn't want to be perceived as coming in in the middle of all of this," he said. Ritchie, a member of the county Republican State Central Committee and a condominium developer in Baltimore, speaks out frequently against what he terms "stupid growth" in Prince George's.

Ritchie said that he spent some time on the phone with Schaefer aides during the week before the event explaining the group's purpose.

"We're not antidevelopment," he said. "We're not opposed to . . . properly planned development."

One of Schaefer's chief local allies, County Executive Glendening, was not present at the dinner. He is one of the civic federation's least-favorite people and is frequently a target when they accuse government officials of being cozy with ambitious developers.

But the Baltimore mayor's popularity in Prince George's seemed the other night to overwhelm any dissatisfaction with the company he keeps.

"Growth is inevitable," Schaefer told the suddenly silent dinner crowd, which included State Comptroller Louis Goldstein, Baltimore City Council President Clarence H. Du Burns and state Sen. Thomas V. Mike Miller (D-Prince George's). "Planned growth is what should be done."

Also present was Largo attorney and businessman Peter F. O'Malley, who was for years the county's most powerful Democratic political powerbroker. Lately, O'Malley has said that he would love to run for governor if Schaefer is not in the race, even though his recognition factor outside of Prince George's is limited.

"After it was over I observed to the mayor that it was purposely staged by us to convince him not to run," O'Malley jokingly said, noting Schaefer's discomfort.

O'Malley said he avoids discussing the political future with Schaefer to avoid having it confirmed that the mayor will definitely be a candidate in 1986. "What my fear is is that it will blow my bubble," he said.