Saddle Run, a 364-acre residential and commercial project in western Prince William County that had been targeted by citizens fighting growth there, was approved by a 6-to-1 vote of the Board of Supervisors at a meeting that ended early yesterday.

The 751-home project is the first major residential development to be approved for more than a decade in the Gainesville area 35 miles west of Washington on Rte. I-66. The developers, Zuchelli, Hunter and Associates, a nationally known land planning firm based in Annapolis, are promoting Saddle Run as an exclusive community for horse lovers.

While many members of the real estate community are heralding Saddle Run as a sign of the vibrancy of the Gainesville market, some residents believe the development will not be compatible with their rural life style. If Saddle Run is approved, "I have no frontier where I can move," said Betty Rankin at the meeting Tuesday night.

But Rankin was nearly alone in her plea. Only one other person at the hearing protested the rezoning, a sign that opposition to growth in western Prince William is wearing thin, county officials and real estate brokers said.

Anne D. Snyder, a veteran civic activist in the Gainesville area, said she was disappointed that 2,000 fliers sent to Gainesville residents flushed out fewer than 20 persons for planning commission hearings on the development. "I fear they are giving up," she said. A petition with 75 signatures opposing Saddle Run was presented to the board.

Not all real estate business people were happy with the board's vote. Oscar Hinshaw, a broker with Key Properties in Manassas, called the vote a "bad precedent for planning" because the county got no cash commitments for schools from the developers, and transportation problems at the site remain unresolved.

"What type of supervisors would vote for a rezoning that doesn't have all the rights of way for the roads it needs? . . . That is the worst planning that I have ever seen in Northern Virginia," Hinshaw said.

Frank A. McDermott, the developers' attorney, said road problems would be resolved when site plans are approved. Moreover, the county has the power to halt Saddle Run's development if access problems remain by refusing to issue building permits, McDermott said.

Voting against the development was Gainesville District Supervisor G. Anthony Guiffre.