When Montgomery County Executive Charles W. Gilchrist took charge of the county bureaucracy four years ago, he was a state legislator inexperienced at management, more practiced in formulating policy than in actually carrying it out. For the daily running of government, he hired Robert Wilson, described by a top aide as "the consummate manager," to be his chief administrative officer.

Now as Gilchrist begins reshaping his administration for a second four-year term, he has emerged as his own chief manager with four years of on-the-job training. He has accomplished, for the most part, his goal of centralizing the county's sprawling bureaucracy--especially the budget planning functions--under a more powerful executive office, and aides say he has adjusted to the often overwhelming workload and spends more time thinking policy and less time shuffling papers.

Last week Wilson resigned his $70,000-a-year job, effective April 8, saying he did not want to make a commitment for another four-year term. With his departure, Gilchrist and his close advisers are freer to decide what role the next chief administrative officer should play in the new administration.

The early thinking over Wilson's replacement is illustrative of how the county government has evolved under Gilchrist, who, with his influential special assistants, has coopted most policy-making and centralized the decision-making process. In doing so, Gilchrist--only the second county executive since the office was created in 1970--has moved toward making the office like that of a big-city mayor to represent the changing realities and increased urbanization of a county of 580,000 people.

Without the pressing need for a "consummate manager," some aides are arguing that the next chief administrative officer should be more of a Gilchrist "alter ego" than was Wilson, a nuts-and-bolts professional admininstrator who had run the bureaucracies of Prince George's and Fairfax counties before joining Gilchrist's team.

"Four years ago, we were looking for someone who had substantial experience in administration," said Gilchrist's special assistant, Thomas B. Stone. "We were looking for someone who would do the day-to-day administering of a huge and rather cumbersome bureaucracy."

Stone said his thinking has evolved to the point where he now believes the next chief administrative officer should be more of "a staff coordinator," implementing policy but not really generating it. Wilson did both.

"It is less crucial to get a consummate manager than it was four years ago," said Edmond F. Rovner, another special assistant and Gilchrist's political point man.

"Charlie himself now has four years of managerial experience. We have an office of management and budget that we didn't have before. We have a strong cadre of department heads who now have four more years of managerial experience."

Some county officials speculated that Wilson's resignation was inevitable with the rise of a powerful budget office and staff, and the addition of the politically savvy and experienced Rovner to the staff midway through the first term.

Rovner had worked in the administration of former Maryland governor Marvin Mandel and as a congressional staff aide.

"Ed Rovner came in and assumed much of the role of a chief administrative officer in terms of thinking out policy," said one top official.

"With budget director Jacqueline Rogers taking over much of the policy programming through the budget process, that sort of cut Wilson out."

Creation of Rogers' budget office was one of the initial goals of Gilchrist's effort to centralize the county government--an effort that included transferring programs and responsibilities between departments.

Under Gilchrist's Republican predecessor, James Gleason, the county's first executive, the bureaucracy largely ran itself, with staffs of long-entrenched professionals and semiautonomous department heads.

When Gilchrist tried to change that system, he ran into opposition from some veteran members of the all-Democratic County Council, who accused him of tampering with the county's strict civil service system and trying to concentrate too much power in the executive branch.

Gilchrist was bloodied in some of his efforts to centralize power in his office. When he tried to move the headquarters of the autonomous and powerful park and planning commission from Silver Spring to Rockville, the council handed him a stinging defeat.

Gilchrist was similarly trounced by the council when he tried to centralize the county's numerous independent fire departments into a single county department.

Besides Wilson, two other high-ranking administration officials have resigned since the election--finance director Albert Gault and director of family resources Harvey McConnell. Gault's departure was a major loss because of his experience and his national reputation as a keen investor of county funds, but otherwise Gilchrist's original team is apparently going to remain intact.