"I understand my timing is perfect," said a grinning Sen. Charles McC. Mathias (R-Md.), walking across the Senate Caucus Room to shake former senator J. William Fulbright's hand. "I just missed your speech."

Fulbright's speech hadn't been that long, but as he, himself, had joked to a roomful of people who had given him sustained applause, "I won't go on too long. You'll think I'm filibustering."

The people who came to see Fulbright, the initiator of the Fulbright Scholarship program, receive a citation on the 50th anniversary of the Experiment in International Living program probably wouldn't have minded. They were, for the most part, alumni of an expansive international exchange program that places youths -- and other individuals -- with families in foreign countries, does development work (such as English language classes for Southeast Asian refugees) and runs the School for International Training in Brattleboro, Vt., Besides the American participants, representatives from a variety of other countries showed up last night.

Also in the caucus room of the Russell Senate Office Building were the directors of the program, the director of the Peace Corps and the host, Sen. Patrick Leahy (D-Vt.), whose home state is headquarters to the program. "One of the things I did as a law student was to come to the Foreign Relations Committee and listen to the chairman speak," said Leahy of Fulbright.

The citation presented to Fulbright read in part: "No one in the past fifty years has had a deeper or longer lasting impact on people-to-people international exchange." Fulbright proposed leaving post-World War II surplus property money in Europe to finance post-graduate foreign studies of Americans -- the Fulbright Program which, since 1949, has awarded more than 137,000 scholarships to both Americans studying abroad and Europeans studying here.

Asked if he missed the Senate, which he left after he was defeated in 1974, Fulbright, a lawyer here, said, "Sure. Well, you miss it in more ways than one. When they tell me about the filibuster on abortion, you miss it the way you miss a splinter you pulled out of your finger . . . I don't think it brings credit to the Senate -- a filibuster on an issue that shouldn't be before the legislative body at all.Abortion is a matter of conscience."

Leahy, too, had some words about the abortion issue when asked what was new in the Senate. "Abortion, Jesse Helms, school prayer," said Leahy. "We're not letting ourselves be sidetracked by unemployment, Social Security, disastrous unemployment. Not for us these minor issues. Not when we can have a constitutional amendment telling us when life begins. Maybe we'll even go back to evolution."

Fulbright and others spoke optimistically of the Reagan administration's encouragement of exchange programs.

"The president has really zeroed in on volunteerism," said Loret Ruppe, director of the Peace Corps program. Ruppe's husband, Philip, a former Republican congressman from northern Michigan, is now running for the U.S. Senate in Michigan. Loret Ruppe, who says her past experience was as a "volunteer, housewife, mother and political wife," was never a Peace Corps volunteer.

"I wish I had, but it's much too tough," she said. "When I visited volunteers, I saw that they were living so happily and so dedicated in incredibly tough conditions. In an age when marriages don't last two years, here are people dedicating themselves for more than two years."