On the afternoon of Saturday, Sept. 7, Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) was in his Capitol hideaway office catching up on paperwork when Secretary of State George P. Shultz unexpectedly called to say, "Dick, I'd like to come over and talk with you about South Africa."

An hour later, Shultz arrived, still wearing the green polo shirt and canary yellow trousers of a golf outing. With Shultz was Chester A. Crocker, his assistant secretary for African affairs and the author of President Reagan's controversial "constructive engagement" policy of friendship for South Africa's white minority government.

In a gesture symbolic of Lugar's increasing influence in U.S. foreign policy, Shultz handed him a draft copy of a White House order imposing economic sanctions against South Africa. After months of resistance, the president finally had been persuaded -- in large measure by the persistent senator from Indiana -- that such action was the best way to avoid an embarrassing defeat by a combative Congress determined to impose even tougher sanctions on Pretoria's apartheid regime.

It wasn't the first time in the 10 months since Lugar became committee chairman that the administration, having boxed itself into a corner, relied on him to find an escape route. The deceptively soft-spoken senator also has hammered out compromises on such sensitive issues as an arms sales to Jordan and aid to Nicaragua's counterrevolutionaries.

In the process, he is leading the Foreign Relations Committee out of the drift and malaise that hobbled it for more than a decade and is restoring much of its luster as a force in foreign policy.

Not much was expected from Lugar last January when he became chairman following the 1984 election defeat of Sen. Charles H. Percy (R-Ill.). Lugar's record on the committee, where he had served since 1979, had been unspectacular; he generally was regarded in the Senate as a pragmatic, slightly right-of-center Republican with respected opinions but a penchant for hugging the background.

"When a leadership spot was up for grabs, everyone tended to think of Dick as a good second or third choice," one Senate colleague said.

Other senators praised his intellect -- Lugar was a Rhodes Scholar -- but they also spoke of his "Boy Scout image." In general, the former Eagle Scout seemed cut from the same gray cloth as his two predecessors in the chairmanship, Percy and the late Sen. Frank Church (D-Idaho).

Lugar has confounded those lowered expectations by displaying a virtuoso ability to stride into confrontations between the administration and Congress and produce an 11th-hour formula for compromise.

Less dazzling, but ultimately more important, has been Lugar's ability to distract Democrats from his staunchly conservative record and inject a bipartisanship into committee deliberations through a capacity to listen to other sides of an argument.

In dealing with a potentially fractious committee membership that ranges from Sen. Jesse Helms (R-N.C.) on the far right to liberals such as Sens. Alan Cranston (D-Calif.) and Christopher J. Dodd (D-Conn.), Lugar wins high marks for fairness.

"He's very charming and very accommodating," Sen. Nancy Landon Kassebaum (R-Kan.) said. "But that doesn't mean that it's a committee of coequals. It goes almost unnoticed, but his way of accommodating differing views always seems to end up with them being wrapped around a position that reflects Dick Lugar's interpretation of the way things should be. It's the mark of a strong chairman that he can do that while maintaining a sense of consensus."

In June, when the administration was about to propose a major arms sale to Jordan despite heavy congressional opposition, Lugar was instrumental in convincing the White House to defer the move and settle for $250 million in economic aid.

Two weeks ago, the administration sought anew to push through the $1.9 billion Jordan arms sale. At the last minute, as opponents were preparing for a showdown in which at least 74 senators were expected to vote against the sale, Lugar suddenly came up with an agreement -- reluctantly accepted by the administration -- to delay the sale until March 1. The compromise passed the Senate 97 to 1.

It was Lugar, working with Sen. Sam Nunn (D-Ga.), who rescued Reagan's aid program for the rebels fighting Nicaragua's leftist government by producing the formula that allowed funding to continue, in the form of "humanitarian assistance."

And it was Lugar, collaborating with Rep. Dante B. Fascell (D-Fla.), chairman of the House Foreign Affairs Committee, who shepherded the first foreign-aid authorization bill through Congress since 1981.

Dodd, who calls that action Lugar's biggest achievement as chairman, said much of the committee's diminished influence on foreign policy in recent years was the result of its failure to agree on legislation spelling out the ways aid funds can be used. When employed skillfully, amendments tacked onto a foreign-aid authorization enable the committee to impose its views across the range of policy decision-making.

The committee's inability to use that weapon gave the executive branch a freer hand. It turned to the Budget and Appropriations committees, which provide aid funding through continuing resolutions that are much less restrictive.

"By frittering away its authorizing function, the Foreign Relations Committee became a largely irrelevant debating society," Dodd said. "In getting a foreign-aid bill through the Senate, Lugar restored some small measure of the committee's prestige and relevance."

In Dodd's gloomy assessment, the committee has a long way to go if it is to recapture the glory days after World War II when it was virtually an equal partner of the White House in defining the bipartisan policy that guided the United States to superpower status. In the mid-1960s, the committee shifted direction. Under J. William Fulbright (D-Ark.), its chairman for 15 years, it became the stronghold of congressional opposition to the Vietnam war. But, after Fulbright's departure in 1974, the committee, hobbled by the lingering divisions of Vietnam and led ineffectively by a succession of weak chairmen, was unable to carve out a new purpose and role.

Defeat at the polls ended Church's tenure after two years. And Percy, who came in when the Republicans took control of the Senate in 1980, was disliked by the inner circle of Reaganites, who undermined his authority by treating him with open condescension and working instead through then-Majority Leader Howard H. Baker Jr. (R-Tenn.).

It was against that background that Lugar took over, determined, as he says, "to get the committee used to working and reasoning together again. My aim was to convince the members, both Republican and Democrat, that if they wanted the committee to be effective, if they wanted to make a record that they could take back to their constituents, then they would have to replace the pervasive sense of partisanship with a new esprit and willingness to find common ground."

He had some important help. Shultz, eschewing the animosity some Reaganites had shown Percy, established a close and cordial working relationship with Lugar that includes regular breakfast meetings and frequent telephone calls. Sen. Robert J. Dole (R-Kan.), who became majority leader in January, has followed an informal arrangement of trusting Lugar to control most of the Senate's day-to-day foreign policy business and to keep him informed.

But the biggest factor has been Lugar's undeviating emphasis on what he calls "consensus and common ground." In search of that, he began by scheduling a series of hearings that ranged across the entire foreign policy spectrum. They were long, frequently dull and attracted little outside notice.

But in Lugar's view "they were an excellent forum for finding out what the members of the committee and, by extension, the other members of the Senate have on their minds. I could see who had a special interest in Greece and Turkey, who in Israel, who in human rights. And that gave us a better gauge of how to assure that these interests somehow get addressed in the committee's work.

"In each of the issues that come before the committee, there's no manual that tells you how to do it," he said. "Each is a situation where you have to play it as it lies. If there's a single rule that I try to follow, it is that we've had a time of confrontation in this country and that we now should look for compromise and accommodation.

"I try to keep that in mind if I'm dealing with my Democratic counterparts or with Secretary Shultz and President Reagan. I support the main outlines of President Reagan's policy, but I've made clear to them that I can't be a rubber stamp. When I tell them I think they're going the wrong way on an issue, it's coming from someone who isn't looking for a confrontation but who wants them to be seen and heard at their very best."