President Carter's long-range foreign policy is gradually, if slowly, beginning to take shape, and if it ultimately succeeds much of the credit ought to go to the self-effacing Secretary of State. Cyrus Vance, who so patiently goes about his business seemingly indifferent to the lack of acclaim he has been accorded, especially by a press that tends to patronize him.

The announcement that Carter is planning a dramatic trip to four continents this fall, plus the progress in U.S. Soviet arms-control talks and the hopeful developments in Arab-Israeli peace negotiations, has naturally inspired a fresh look at the administration's foreign policy, but Vance's expanding role still attracts relatively little attention.

This is hardly surprising considering that Carter is very much his own spokesman on foreign policy. And when he himself is not expounding the administration line, two other highly vocal advisers - Zbigniew Brzezinski and U.N. Ambassador Andrew Young - can be counted to fill in.

Nevertheless, Vance in his quiet way has been all over the scene recently, culminating at the United Nations, where, in the last week, he has conferred with scores of foreign leaders on an endless array of issues.

Meanwhile, he found time to testify persuasively before the Senate Foreign Relations Committee in behalf of the Panama Canal treaties, to help work out with Andrei Gromyko, the Soviet foreign minister, an extension of the strategic arms limitation agreement, and, among other things, to encourage Israel to give new and more favorable attention to the U.S. formula for getting the Geneva peace conference back on the tracks.

It was a good week's work, the kind that would have resulted in Vance's scintillating predecessor, Henry Kissinger, being treated like a matinee idol. The current Secretary, however, seems to be content if ther press just spells his name correctly.

By this time, Vance is getting used to being called "colorless" and the "Calvin Coolidge of diplomacy." Because there have been few, if any, dramatic foreign breakthroughs in this still-young administration, he has heard himself referredto as a "no-win" Secretary, and a "figurehead."

It's not too hard, though, for an official to tolerate such denegration when he knows, as Vance does, that he has the confidence and the ear of the President.

Another factor that sustains the State Department chief is that, even before taking office last January, he understood and sympathized with one of Carter's paramount objectives, which, in the President's own words, is to free the United States from its "inordinate fear of communism."

Like Carter, the Secretary believes in dealing with all countries, including China, Vietnam and Cuba. As he told a recent interviewer. "Walling ourselves off so that we don't talk to other countries is very, very bad and unsound policy." And he added. "I believe that these sharp cold-war issues that have existed in the past are detrimental and we should move away from that type of foreign policy."

Carter, in turn, feels comfortable with Vance because, for one thing, the Secretary has the political savvy to realize that it is going to take time - at least several years - to disengage the United States from all the far-flung, costly involvements that we assumed during the height of the cold war.

Vance has turned out to be just about what Carter wanted in a Secretary of State: intelligent, rational, cautious, patient, even-tempered and highly experienced. Not a yes-man, but a congenial and modest adviser.

The President is also said to appreciate the uncomplaining way that Vance has carried out no-win missions, such as going to Moscow for arms-control talks just after Carter's human-rights attack on the Kremlin and later going to the People's Republic of China in the wake of Carter's statement that he was in no hurry to recognize Peking.

Despite these handicaps, Vance did his effective best to smooth things over, to keep communications open while reassuring the Communist superpowers of friendly U.S. intentions and finally to play for time. All this is now paying off, as can be seen from the way Moscow is relaxing and gradually coming around to Carter's overtures on SALT and detente in general.

The trips that the President sent Vance on to the Middle East also looked like no-win missions at first, but the trust and good will he generated appear to have paved the way for the constructive follow-up talks the President has recently had in Washington with visiting leaders of the region.

Carter is going to have his hands full with the nation's cold warrior, who are now banding together to oppose the whole thrust of his emerging policy. Nonetheless, they do not seem disposed to go after Vance as the rightwingers of an earlier day attacked Harry Truman's brilliant but abrasive Secretary of State, Dean Scheson.

The discreet Vance is not likely to draw that kind of fire, for which Carter will be grateful when the going gets really tough on Capitol Hill over SALT, over the Korean withdrawal, over Panama, or normalizing relations with Cuba and Vietnam, over recognizing China and shedding Taiwan. The Secretary of State was born not to arouse wrath, but to turn it away. It's a good bet this prestige will grow the longer he remains in office.