William D. Ruckelshaus, President Reagan's choice to head the Environmental Protection Agency, met yesterday with more than two dozen environmental leaders in a session that the environmentalists characterized afterward as long on topics but short on specifics.

"I don't think you could say it was fruitful. It was frank," said Richard Ayers, senior attorney for the National Resources Defense Council. "He studiously avoided making any policy commitments."

Ruckelshaus, whose Senate confirmation hearings have not been scheduled, was not available for comment after the meeting. He has avoided public appearances and press contacts since he agreed last month to return to the agency, which he served in the 1970s as its first administrator.

According to environmentalists who attended the meeting, Ruckelshaus was attentive and took notes while they laid out a list of concerns ranging from the agency's dwindling budget to the industry ties of some of its top officials.

But the discussion struck a discordant note on the subject of enforcement activity, including lawsuits against alleged industrial polluters.

According to several participants, Ruckelshaus, a vice president of Weyerhaeuser Co., called lawsuits a "resource-intensive" remedy of use in "flagrant cases" and said he didn't want to see industry become a "scapegoat" for environmental ills.

"When pressed, he said he was very concerned that the rights of private parties be protected," said Ayers. "I was concerned that 'scapegoat' was the first word to issue from his lips."

J. Michael McCloskey, executive director of the Sierra Club, said the response "added up to nothing that indicated he intended to step up enforcement . . . . We were hoping to hear him say that it was time to get a tougher EPA back in business."

Ruckelshaus also sidestepped frequent invitations to state his positions on pending legislation affecting the agency, including the Clean Air and Clean Water acts, or on administration proposals for more budget and staff cuts at the EPA.

"It left you wondering whether he really does feel he has the latitude to do what he says," McCloskey said.

Of intense interest to the environmentalists was Ruckelshaus' potential relationship with Interior Secretary James G. Watt, who as head of the Cabinet Council on the Environment is a chief architect of environmental policy. Ruckelshaus reportedly said he did not intend to cede ground to the controversial Watt, but added that there was "nothing to be gained by getting into fights" with him.

Despite the lack of specifics, environmentalists said they were heartened by the meeting, the first such get-together during the Reagan administration.

Bill Butler, a National Audubon Society official, said Ruckelshaus told the group that "all decisions--on the budget, personnel and policy--are open. He set himself up for great opportunity and great criticism . . . . He can't say he inherited a policy."

Gaylord Nelson, former senator from Wisconsin and chairman of the Wilderness Society, noted that Ruckelshaus "said he intends to carry out the mandate of the Congress. That, of course, is a dramatic departure from the past two years."