Long before the Montgomery County school board voted last week to close Rosemary Hills Elementary School in Silver Spring, the school's fate was sealed.

What transpired in the days before the voting was a well-orchestrated move by four conservative board members led by Joseph R. Barse. Working by telephone and from like-minded philosophies, they formulated a detailed plan to break up the pairing of the Rosemary Hills school in a predominantly minority-race area, and Chevy Chase elementary, located in a mostly affluent white neighborhood.

That pairing had been adopted by a different board five years ago and was the county's first significant attempt at busing for racial integration. The Rosemary Hills area has always been racially mixed, and its school became the symbolic focal point of the county's attempts to integrate its schools.

Thursday's vote was the board's most dramatic move so far to alter the school busing plan. The victory also was the crowning achievement for the year-old conservative coalition. It was accomplished through well-plannned and pragmatic politics, and illustrated the growing power and sophistication of the school board's new majority.

By operating out of the public eye, as they have done frequently on school closings and other controversial issues, the four conservatives were able to assure the breakup of the Rosemary Hills-Chevy Chase pairing.

Without violating the sunshine laws, which prohibit four school board members from convening without issuing a public notice, the four board members have maneuvered behind the scenes to take a series of actions that have changed drastically the school system's policies on several racial issues. Often they have acted without the knowledge of board President Carol F. Wallace, although she usually votes with them.

In some instances, according to school board sources, two or three in the conservative group simply have discussed a matter by phone, leaving one of them in charge of drawing up a memo of their plan. During the past three weeks, however, that has gone one step further. Barse has acknowledged meeting with board member Marian L. Greenblatt on weekends to review ideas, and presumably to plot strategies.

Greenblatt and Eleanor D. Zappone, another member of the coalition, live within minutes of each other and often drive together to Wheaton High School, where the board votes on school closings.

The evidence of synchronization is apparent even at the public meetings. Sitting across from each other at the board table, Greenblatt and Zappone often can be seen exchanging nods of approval or disapproval before a vote is taken.

Three days before the Rosemary Hills vote, Barse submitted to the school system staff and all board members a comprehensive memo outlining his proposal to close Rosemary Hills and to assign its students to three schools in the Bethesda-Chevy Chase area, excluding Somerset elementary, which is in Barse's own neighborhood and is underenrolled.

On Thursday afternoon, hours before the vote was taken, Greenblatt, one of Barse's allies, telephoned board vice president Elizabeth Spencer to discuss a different school matter. Greenblatt never brought up the issue of Rosemary Hills with Spencer, a member of the board that had created the pairing in 1976 and whose interests in integration efforts are well known.

The board's 5-to-2 vote was directly at odds with the recommendation of the school superintendent and it took many by surprise, including Rosemary Hills principal Dru Stafford, who with other faculty members watched the action from the audience.

Although Greenblatt had proposed in September that Rosemary Hills elementary be considered for closing, the move last week elicited emotional responses from Spencer and board member Blair Ewing, the two who voted against it. Ewing, as he has done frequently, criticized his colleagues and charged that the board "doesn't give a damn about minorities."

A veteran in the school system, Spencer delivered a stinging attack on Barse, Greenblatt, Zappone, and Suzanne Peyser, who make up the conservative coalition. Without mentioning names, she implicitly singled out Greenblatt, the undisputed leader of the conservative bloc, for directing the political machinations.

Spencer reported that there had been "rumors" circulating all week about "deals" that were made behind the scenes to protect the special interests of "certain" board members.

For Ewing, Spencer and some other school system staff members, the evening culminated a series of actions by the conservative majority that began last year to change the picture of school policy in the county.

With Greenblatt leading most of the coalition's actions, the board has been forced to change the county's acceptable ratio of minority students in schools, abolish a minority affairs committee, appeal to the Reagan administration on the issue of busing and change school boundaries that would have improved racial balance at Blair High School, which has the largest minority enrollment of any high school in the county.

At the same time, Barse's neighborhood was spared any dramatic changes when boundaries were redrawn last week. And so far Greenblatt's and Zappone's elementary school area, which is slated to have a slight increase in minority students, has yet to be voted upon.

On the Rosemary Hills closing, Barse and his allies had what they termed "objective" arguments prepared in advance. They rejected charges that any of their actions were racially motivated, and emphasized that the Rosemary Hills plan would actually improve racial balance in the overall area.

The bottom line, they said, was that the Rosemary Hills-Chevy Chase pairing was an experiment that had failed. "It's time for a change," Greenblatt explained.

The board majority's message was tailor-made for certain elements of the Chevy Chase community, where parents have been complaining more and more during the past five years that their children were not flourishing in a setting with so many children from lower socioeconomic levels.

The end of the five-year-old busing plan is defended by supporters as educationally sound because children will attend only one school through sixth grade, fiscally wise because money will be saved when Rosemary Hills is closed, and racially fair because more schools in the Bethesda-Chevy Chase area will be integrated.

But Ewing said these arguments are simply "a red herring."

"It's not old-fashioned bigotry," he said. "It's just taking actions that ignore the minority community, and it is a recipe for chaos."