Moshe Dayan's departure from the Israeli Cabinet appears to signal a decision by Prime Minister Menachem Begin to draw a firm line against any further significant concessions to Egypt or the United States on Palestinian autonomy.

In sharp contrast to his open dependence on Dayan as recently as six months ago, Begin put out little effort to keep in office the one Cabinet member who has given the Likud government the international stature it has desperately needed.

A more hawkish approach by Begin on the stalled negotiations with Egypt could lead to complete stalemate and perhaps endanger the entire peace process. There seems little likelihood that Dayan's moderating influence can be effectively supplied by anyone else.

The fact that Begin made three desultory attempts to convince his foreign minister to remain in the governemnt little diminishes Begin's readiness to break away from his compelling reliance on Dayan during the first half of his elected term as prime minister.

Despite the vast gulf between their ideologies, Dayan was a crutch for Begin. He was the one Cabinet member who gave the Likud government the international recognition it so desperately needed when Begin was swept into office virtually unknown to the world outside Israel except as a feisty former guerrilla leader from prestatehood days who spent 29 years carping at the Labor government from the back benches of the Knesset.

It is true that Begin brought into his Cabinet other illustrious figures from the old guard establishment that for nearly three decades had condescendingly tolerated the amusing rightwing opposition leader, among them Yigael Yadin, Begin's deputy premier.

But Dayan's role in the Cabinet was not merely to give the Likud government international stature and to legitimize in the world arena a leader who had been on the outside looking in since the founding of the Jewish state.

Dayan quickly became a powerful force in the Begin Cabinet, a strong right hand not only in the shaping of foeign policy but also in domestic matters. Although he occasionally grew impatient with his mercurial and at times ill-tempered foreign minister, Begin developed what many Cabinet ministers saw as a psychological dependency on Dayan.

Dayan held the prodding stick to Begin, constantly pushing the prime minister inch by inch from intransigent positions and initiating new diplomatic processes.

He often did it in unorthodox ways that infuriated his ministerial colleagues, but in the end Begin usually yielded to the prodding and then came to be grateful to his foreign minister when the rewards became apparent.

For example, in April 1978, when Egyptian President Anwar Sadat's historic visit to Jerusalem six months earlier was beginning to look like a passing aberration, Dayan casually associated the West Bank with U.n. Resolution 242, by dropping one of his typical "sleeper" policy shifts in a little-noticed television interview.

Dayan said the U.N. resolution calling for Israeli withdrawal from territories occupied in the 1967 Six-Day War applied to territory captured from all of Israel's neighbors, including the remark surely was a surprise to virtually the entire Cabinet. Although much of the world press was slow to grasp the significance, Dayan was clearly signaling a softening of Israel's position on negotiation the future of the West Bank.

While Dayan's free-lance observation hardly seems monumental today, considering the extraordinary events of the last year, it paved the way for a resumed dialogue with Egypt and, ultimately, to the beginning of the Camp David peace process.

There have been numerous other examples since then where Dayan deftly and subtly proded Begin into large and small concessions, sometimes privately and sometimes by going public to generate controversy as an inducement.

The most recent example of Dayan's efforts to instill life and flexibility into the Cabinet's hard-line positions came when Dayan unilaterally and without informing Begin opened a dialogue with militant West Bank Palestinia leaders, including outspoken Palestine Liberation Organization supporters.

He also publicly suggested, to the chagrin of Begin and the Cabinet's hard-line members, that Israel should give the moribund West Bank-Gaza autonomy negotiations a jolt by arbitrarily withdrawing the military occupation government from Arab cities and replacing it with a civilian administration.

When it became clear to the prime minister last spring that his maverick foreign minister was breaking barriers too quickly for his conservative coalition, Begin attempted to rein in the momentum through a set of sharply restricted negotiating principles, which included a demand for ultimate Israeli sovereignty over the West Bank and Gaza.

The guidelines, to Dayan's dismay, also declared that Israel would retain control of water on the West Bank, and that Jewish civilian settlements would proliferate with Israeli law, not Arab law, applying to the settlers.

As an additional restraint, Begin saw to it that not Dayan alone but a diluted six-man bargaining committee, carefully supervised by a ministerial policy-making committee, would control Israel's bargaining policy in the autonomy talks.

With hindsight, it is obvious that Dayan must have decided then that his days in the Likud government were numbered, and a close Dayan advisor said as much this week. But even then, Begin continued to lean heavily on his foreign minister in making policy decisions large and small, and Dayan remained the most influential member of the cabinet.

For instance, it was Dayan who last month persuaded Begin, over the advice of many of the prime minister's advisors, to snub the American blackk activist, Jesse Jackson, when Jackson made a highly controversial visit here espousing Palestinian independence. At the time of that decision, amid growing dissension in the Cabinet on many issues, a Begin aide said, with some exaggeration but not without a kernal of truth, "three people are running this country -- Begin, Dayan and Begin's secretary."

But when Dayan, by his own account, started privately suggesting to the Cabinet that there should be an alternative to ultimate Israeli sovereignty over the West Bank and Gaza Strip -- an act of heresy to those whose mystical approach to the occupied territories lies with Israel's Biblical right to the "Greater Land of Israel" -- Begin's strong need for Dayan inevitably weakened and the handwriting was on the wall.

With Dayan voting against expropriation of private Arab land for the controversial Elon Moreh settlement and urging Restraint in the government policies, the distance between the two men grew, and the likelihood of Begin's refusing to accept a Dayan resignation diminished.

Although Yadin is rumored to be a leading candidate for the foreign ministry portfolio, Begin has not yet even consulted with the various coalition factions about a replacement.

Moreover, Yadin's moderate stance and liberal credentials would surely be constrained by the same factors that finally forced Dayan to leave public service at the apex of his career.

The autonomy negotiating team, headed by the conservative interior minister, Yousef Burg, and kept in check by Begin's written negotiating principles and by the 11-member policy advisory committee, would hardly be allowed by Begin to break the kind of new diplomatic ground that Dayan was breaking.

And if Burg, whom Begin would like to appoint foreigh minister because of compatible and equally conservative positions, does get the post, a more flexible bargaining position could be expected.