In the first months of President Reagan's term, the pattern of White House decision-making has been bedeviled by a contradictory impulse similar to one that plagued other recent administrations.

The contradiction is between the president's commitment to Cabinet government, which worked for him during the better part of his eight years as governor of California, and the convenience of making personal decisions with the aid of a small and trusted staff.

Some of the president's most important actions in behalf of his crucial economic program were decided outside the Cabinet, guided by Office of Management and Budget Director David A. Stockman.

Other decisions, such as Reagan's pardoning of two high former FBI officials and the lifting of the Soviet grain embargo, were largely personal ones, made by the president with the timing guided by White House counselor Edwin Meese III or chief of staff James A. Baker III. On these issues, the Cabinet was informed but played no decision-making role.

Only a few decisions, of which the controversial proposal to cut back Social Security is the most conspicuous, have come directly to the president through the sub-units of the Cabinet known as Cabinet councils, the way the system works on the Social Security recommendation, which did not receive the careful political attention given to issues decided outside the Cabinet, is not a happy augury for this process.

Some senior White House aides acknowledge that the Cabinet councils have yet to function as envisioned when formed on Feb. 26. But they contend that the councils are evolving, and that the process was unavoidably delayed by the president's injury in the March 30 assassination attempt.

The president is the chairman of each of the five councils, and decisions were postponed during his recuperation.

The week of the shooting, the Cabinet Council on Natural Resources and Environment, of which Interior Secretary James G. Watt is the chairman pro tem, brought up a controversial proposal to lease Outer Continental Shelf lands for oil drilling off California.

Vice president Bush chaired the council meeting, in Reagan's absence, but the decision was deferred until the proposal could be presented to Reagan, as it is likely to be late this week.

"You don't make decisions without him there," Ronald B. Frankum, deputy director of policy development in the White House, told a recent seminar on the Reagan presidency.

The day after Reagan was shot, the senior White House staff "Triumvirate" of Baker, Meese and deputy chief of staff Michael k. Deaver proclaimed publicly that the watchword for the administration was "business as usual." It was an overstatement, unintentionally suggesting that the president, then flat on his back recovering from a bullet wound, played only an incidental role in his administration.

In fact, as the progress of the economic program Reagan's return suggests, the administration needs the active participation of its president to be effective. Even so, the "business-as-usual" slogan was a remarkable demonstration of the authority and self-confidence shown by the White House Triumvirate.

Reagan's continuing recuperation has increased that authority, at least temporarily. Cabinet government requires more time and the participation of more people than decision-making with a few top aides. And Reagan's access to members of Congress and other outsiders, extensive before the shooting, has been reduced while he works a half-day schedule.

The Triumvirate would argue that a strong staff does not necessarily mean a weak Cabinet.

Speaking to the American Society of Newspaper Editors, Baker said: ". . . It's our feeling that a strong Cabinet and a strong staff are not necessarily mutually exclusive, that they're not necessarily inconsistent and that you can have a strong White House staff whose goal and purpose is to support both the president and the Cabinet."

Baker went on to describe the "spokes-of-the-wheel" system, a phrase used by President Ford's first chief of staff, Donald Rumsfeld. This system is supposed to give a number of senior assistants direct access to the president, whom they can walk in on at any time. It was a system tried out also by President Carter and rejected from the outset by Reagan, who feels most comfortable with a small group of trusted aides.

"Our system is a return to the chief of staff system . . . where every appointment and every piece of paper comes from one central point or one central funnel before it goes in to the president," Baker said.

If the Triumvirate is a funnel, the Cabinet is a forum where everyone can be heard, and where the rule is supposed to be that no members discuss elsewhere what went on inside the meeting.

It has the advantage of reducing tunnel vision and of giving everyone a broad view of the direction of the administration, but it also uses up valuable time of the most important members of the government. Some Cabinet members who might not otherwise be centrally involved in some of the most important decisions, such as Secretary of Commerce Malcolm Baldrige and trade representative Bill Brock, are enthusiastic about the system.

"I've never seen Cabinet government work," said Brock, who has had dealings with half a dozen presidents. "I've heard people talk about it, and I've seen them try it, but I've never seen it work. This time, to date, it's not only worked, but it's worked better than the preceding operations I've seen in the last 20 years."

The Cabinet broke from the gate at a blazing pace. In the administration's first week the 18-member Cabinet met four times. But the pace proved exhausting. Cabinet members found they were spending too much time on issues not directly related to their departments.

There also were complaints that the number of participants made the meetings too unwidely and that too much White House staff time was being chewed up by paperwork before and after the meetings.

These complaints spurred the development of the five Cabinet councils, a proposal drawn up by Meese. It was an attempt to maintain the system that Reagan used in Sacramento and wants to continue to Washington, but without the unwieldiness that undermined past attempts at Cabinet government.

Reflecting the focus of the administration, the functioning of the councils has been uneven. The Council on Economic Affairs has met 17 times, and the council on Human Services only twice.

The other three councils -- commerce and trade, natural resources and environment and food and agriculture -- have met four or five times each. For organizational purposes, the National Security Council, which has been scaled down in stature by the Reagan administration, is also regarded as a Cabinet council.

All councils have a Cabinet member who can chair in the president's absence. There is a standing rule at all councils except the NSC that any Cabinet member interested may attend a session, whether or not he is a member of the council.

After a council has made a recommendation, the president may make a decision on the spot or take the issue under advisement.

One advantage of having the president make a decision in this setting, as Meese explained it to the editors, is that it reduces second-hand interpretation and the "suspicion and often hostility" which in the past characterized relations between White House staffs and those outside the decision-making process.

But on the politically sensitive issue of Social Security, the system did not function in a textbook manner.

For weeks, a variety of short-term and long-term changes had been under examination in Richard S. Schweiker's Department of Health and Human Services. The review was directed by his undersecretary, David B. Swoap, who had helped implement Reagan's welfare reforms in California.

Schweiker had pledged that the administration would make its proposals known to Congress, and he wanted to do this before mark-up began in a committee on a bill proposed by Rep. Jake Pickle (D-Tex.).

While the options had been studied extensively by Schweiker and Swoap, the White House had not focused on them. Meese was not briefed until May 9, a Saturday, two days before the council on Human Resources met. Reagan was known to be reluctant to accept any proposal that would be perceived as a retreat from his campaign pledge not to reduce the benefits of people already receiving payments. The proposal would, in fact, reduce these benefits, although the brunt of the cuts fell on people who were near early retirement.

But there was a selling point that may have proved irresistible. It was an argument, first advanced to the Reagan White House by President Ford's one-time economic adviser, Alan Greenspan, who said the financial markets were not responding to the Reagan economic program because it was directed at easy targets. Cutting Social Security would show that Reagan meant business.

The options were discussed for an hour May 11 in the Cabinet Council on Human Resources. Martin Anderson, director of the Office of Policy Development, spoke up in favor of the proposal. Reagan, chairing the meeting, was still uncertain. After an hour of discussion he adjourned the meeting without decision.

But that afternoon, after a brief meeting with Meese and Baker, Reagan called Schweiker back and said he had decided to go ahead with the proposal. Baker, his staff director, David Gergen, and deputy press secretary, Larry Speakes, informed the wire services, the networks and selected newspapers about the major elements of the decision.

What had happened was that a decision whose policy implications had been considered in detail by Swoap and Schweiker had flashed only briefly on the political radar screen at the White House and had been decided too casually and quickly.

No systematic feedback had been obtained from Reagan supporters on Capitol Hill by legislative liaison Max Friedersdorf, who was not informed in advance of the scope of the decision.

Sen. William L. Armstrong (R-Colo.), a knowledgable senator on Social Security issues for whom Swoap had worked as legislative director, supported the substance of the administration proposal, but said he was surprised at its scope and thought the timing disastrous, because it gave the Democrats an issue when they needed one most after their budget defeat.

The Cabinet council system, although working more or less the way it was supposed to, may have contributed to what is now seen as a major White House political blunder. The system tends to leave the development of policy in the hands of experts, without subjecting their ideas to the tests of the political process.

Usually, a major change of the sort envisioned in the Reagan Social Security proposals requires a lot of seed-sowing in advance, both on Capitol Hill and in the press. Such political preparation was almost nonexistent in this instance.

Whether the Reagan experience on this issue will cause changes in the system is not yet clear. The president has a dogged commitment to Cabinet government, and he has shown, repeatedly, that he takes his own campaign promises seriously.

No matter what system of decision-making he uses, Reagan also has a proclivity for making far-reaching proposals that cost him the support of his party, and then backing off if the reaction is too adverse.

He did this early in his administration in California when he proposed 10 percent budget reductions for all of the state's mental hospitals and quickly related after the outcry. Usually, he comes back with a more subdued version of his original proposal.

But it seems probable, as more and more proposals come to Reagan for decisions, that the convenience of the funnel of his senior staff will gain advantage over the forum of the Cabinet and its councils. Whether the councils are the wave of the future in the Reagan administration will depend upon how well they function in comparison with this handy alternative.

The personal harmony of the Triumvirate his reinforced a tendency to keep the circle small. It is likely to remain that way unless a conscious attempt is made to broaden it.

One White House official outside the Triumvirate said that he has noticed a growing disposition of the Big Three to solve problems among themselves whenever possible. He gets the feeling that outsiders are not welcomed, and he understands why.

"It's easier to deal with three people," this official said.

This is a judgment that may also be reached by Ronald Reagan.