Financially pressed Michigan State University shelled out more than $3 million last year to "buy out" 100 tenured faculty members, figuring the staff reductions would save money in the long run.

Temple University in Philadelphia and the University of Washington in Seattle are giving professors incentives to retire at age 55.

Meanwhile, Regis College in Denver is starting a program to persuade some faculty members to change jobs in mid-career, hoping to open spots for younger scholars and relieve a "bulge" of older faculty members who were hired in the expansion years.

Whether because of hard times or because of an age bulge that leaves little room for new blood, college administrators are pressed to come up with ways of forcing turnover among the nation's 450,000 full-time professors.

At the recent annual meeting of the American Association of University Professors (AAUP) here, talk about the economic "contraction" on campus and its effect on tenured faculty was pervasive. Discussion also dwelled on what to do about a "lost generation" of academics, scholars who are leaving the profession because of dwindling tenured jobs.

The number of tenured professors nationwide has grown in the past several years. AAUP statistics show that 65 percent of college professors are tenured, but the figure could be considerably higher because an increasing number of nontenure-track teaching jobs is included in the statistics.

Irving J. Spitzburg Jr., AAUP's general secretary, said, "The problems are very real. Short term, there is a potential for real disaster if there is too dramatic a retrenchment." Thus his group is pressing for voluntary programs, like those at Michigan State and Washington, to fend off layoffs and forced resignations.

Walter Metzger, professor of history at Columbia and an AAUP activist, said colleges are in better shape financially to face cuts today than they were in the depression of the 1930s. But there are more older professors today because of the "rather extraordinary expansion"--a tripling of faculty members--in the 1950s and 1960s, he said.

"We can anticipate an exodus of massive proportions at the end of the decade," he said.

At Columbia's history department, for instance, he said, "We'll all be gone by 1992." The challenge for administrators is to survive their current financial woes and still add new people now to take over as experienced professors later. "They can't wait until 1992 and find 30 Arnold Toynbees," Metzger said.

Administrators express the same concerns. Jack Peltason, president of the American Council on Education (ACE), a college umbrella group, said the general age-bulge problem will be exacerbated by the change last week in the mandatory retirement age to 70.

Tom Emmet, special assistant to the president at Regis, said he viewed the mid-career change plan at his college "as faculty development. It's a crisis prevention program, not a crisis management one like at Michigan State."

In the mid-career plan, Regis offers faculty members counseling, a year's pay and all fringe benefits, and, the second year out, a $3,000 payment "as an additional boost," Emmet said.

In return, the professor agrees not to go across town and start teaching college courses. "He or she can be a consultant, drive a bus, anything but teach college," Emmet said. For instance, an English professor who volunteered for the program is running an art store.

Emmet, who holds seminars for ACE, said Regis also offers a phased retirement plan to cut workload and pay "so faculty members can feel there is something beyond the River Jordan."

At Michigan State, economics professor Mordechai E. Kreinin developed the buy-out plan in early 1981 in the face of threatened layoffs. He and the administration there are working on what he calls a "social contract," a contingency plan to head off a recurrence of the financial crisis. For instance, he said, professors might agree to take sabbaticals at half pay, rather than pass them up.

At the University of Washington, assistant provost Steven Olswang said that in one economy move there the state legislature passed special legislation to let professors retire at 55 with no loss in benefits. He said he expects more than 100 of the 800 faculty members eligible to take early retirement. That will cost the state more than $500,000 a year in added retirement costs, but will save an estimated $3 million a year in salaries.

Olswang said officials at his school "have a great fear" that a current hiring freeze will kill off a new generation of faculty. So the University of Washington also is offering a phased retirement plan that it hopes will double the school's normal turnover rate and make room for new scholars.

Emmet said less than 10 percent of the nation's 3,000 colleges and universities have tried to alter the traditional faculty career track, but he expects more schools to experiment with changes in the future.

"There will be fewer Chipsian (as in Mr. Chips), one-career faculty members," he said. "There are more and more part-timers, and there is a new group emerging, people who have two careers. It will change our entire thinking on how we pay people and provide benefits."