Fairfax Deputy County Executive Anthony H. Griffin, who was passed over for the county's top job two years ago, won the post yesterday after vowing continued efforts to reform the county's massive bureaucracy and keep its financial house in order.

Griffin, a former U.S. Marine who got his start in local government as an aide in Arlington County 25 years ago, will succeed former county executive Robert J. O'Neill Jr., who resigned abruptly last month after a two-year tenure to head a government think tank. Having been given a mandate to reinvent county government, O'Neill was frequently stymied in his efforts.

Yesterday, members of the Board of Supervisors said they expect Griffin to pick up where O'Neill left off: linking raises to performance; privatizing many government functions; making better use of technology; and efficiently managing the budget.

"We like what Bob O'Neill started, and we want to continue it," said Supervisor Gerald E. Connolly (D-Providence), an ardent Griffin supporter. "We're confident he will serve as a change agent, even though he is an insider."

In choosing Griffin--a 10-year veteran of the county's bureaucracy--on a unanimous vote, the supervisors rejected the idea of conducting a lengthy nationwide search for an outsider to fill what many consider a plum job. Fairfax, with a population of close to 950,000, is among the country's biggest and wealthiest counties.

Several officials said privately it was unlikely that any search--no matter how broad--would net a better candidate than Griffin, who was a finalist, along with O'Neill, for the job in 1997. He had held the position in a temporary capacity for about nine months in 1996 and 1997 after a previous county executive was fired.

"We know Tony. Tony knows us. This was clearly the way to go," said Supervisor Penelope A. Gross (D-Mason).

Yesterday, supervisors also said they were afraid Griffin, 52, would leave the county rather than submit to another round of interviews. But some Republicans, who had indicated a desire to conduct a wide-ranging search for a new executive, were less enthusiastic.

Supervisor Michael R. Frey (R-Sully) was lukewarm in his endorsement. "Given the makeup of the board, clearly this was the direction the board was going," Frey said. "I think Tony will be fine."

Griffin's appointment, effective Jan. 15 pending salary negotiations, came after a 30-minute closed-door discussion between him and supervisors that participants later described as "cordial." After the announcement and a round of applause, Griffin said he plans to be in Fairfax for many years and promised to finish what O'Neill started.

"I think the kinds of things that Bob O'Neill initiated were great for the organization and should be continued," Griffin said after his appointment, which he said he had not expected yesterday. "Because I'm the, quote, insider, that doesn't mean we're going back to the way we did business here years ago. The intent is to keep the organization moving forward."

Members of the civic and business community praised Griffin's initial comments.

But Chamber of Commerce President James Dyke was cautious, saying his group wants solid evidence that Griffin won't be satisfied with the kind of government he has been a part of for the past decade.

Dyke said his membership, which includes some of the biggest county businesses, wants a county executive who is pro-business and open to privatization, merit pay for county workers and new ways to use tax dollars more efficiently.

"We think it's important that he make it clear that he is prepared to take the bold action we think is necessary that assures our success and prosperity," said Dyke, who plans to meet with Griffin next month.

Several others predicted that Griffin may have trouble following through on O'Neill's initiatives. In his efforts to make government more efficient, O'Neill often ran into opposition from employees, community interest groups and sometimes the supervisors themselves.

When he tried to combine the recreation department with the Park Authority, for example, supervisors killed the idea because of pressure from parks advocates.

"O'Neill's problem was the politics," said Jack Herrity, a Republican who is a former chairman of the Board of Supervisors and who supports Griffin. "I'm not sure Tony can solve those any more than Bob could."

And privately, several people said they weren't sure how committed Griffin will be to the degree of change O'Neill sought, despite Griffin's comments yesterday.

"Tony is going to be a little more concerned with the existing culture of the county," one senior county official said. "He'll be a little less likely to launch off into uncharted directions. It will be a bit of a cooling off."

Democrats, who currently hold a 6 to 4 majority on the board, said Griffin talked yesterday at length about the need to extend rail to the Dulles area, improve traffic conditions at Tysons Corner and continue O'Neill's efforts to revitalize sagging areas on the county's eastern end.

Griffin, who worked for the county during two recent budget crises, said his job will be to ensure that the county is stable if the economy turns sour again.

"I'm extraordinarily fortunate to take over when the county is doing okay economically," he said. "My challenge is to make sure the organization stays in that kind of position for the long haul."

After working with three county executives during the '90s, several supervisors said they expect Griffin to stay in the job for a while, and Griffin said he planned to comply.

"I have an incentive," he said dryly. "It's called retirement."