Virginia Republicans sidestepped a potentially bitter split between moderate-conservatives and hard-core Reaganites today by overwhelmingly approving a compromise slate of delegates to the party's national convention.

The compromise list of 21 at-large delegates, hammered out in a grueling closed-door session lasting until 5:30 this morning, includes a number of party leaders and a former George Bush lieutenant who some Reaganites believed should be exlcuded because they were tardy in boarding the bandwagon of Ronald Reagan, the GOP's likely presidential nominee. As a result of today's action's, Reagan seems assured of all of Virginia's 51 convention delegates.

To make room for the moderates, Reagan campaign leaders agreed to scrap several longtime Reagan loyalists, foremost among them former U.S. Sen. William L. Scott of Fairfax.

Scott, who was Virginia's first Republican senator since Reconstruction and one of Reagan's earliest Senate supportes in 1976, got the bad news this morning from John Anderson, Reagan's state coordinator. Scott then left the convention hall and was not available for comment.

"He said he would have preferred [to go to the national convention in Detroit next month]," said Alderson. He added that Scott's exclusion was "just a question of political realities. . . everyone here is for Ronald Reagan and it's a question of selecting those people who will most help his election."

Virginia Gov. John N. Dalton, who, as expected, was named to the comromise slate despite the fact he did not endorse Reagan until late March, said he was surprised at Scott's removal: "I would have thought he'd be on it if he wanted to go," said Dalton.

Others expressed their disappointment more strongly. "it was really bad form and I'm quite amazed," said Del. Robert Harris (R-Fairfax). Harris said Scott was sacrificed to make room for members off what he called the "new right" including fundamentalist Christians and antiabortionists who some some Republicans fear are attempting to take over the party.

"You've got this new right group here in spades and some of them have been put on the slate in order to pacify them," said Harris.

Another victim of the compromise was Lorna Hadlock, state chairman of the Young Republicans who lost her at-large seat but was named an alternate delegate instead. Hadlock, another longtime Reagan backer, said she was disappointed. Other Young Republicans complained that with Hadlock's removal, no one on the delegation was under 34 and the average age of the delegates was 50.

But many Republicans did not object to the compromise slate noting that Bush supporter Fitzgerald Bemiss of Richmond and Doriene Steeves of Annandale, president of the state Federation of Republican Women, both made the slate despite hard-core Reaganite opposition.

"I suspect Doriene Steeves will make a lot more phone calls for Ronald Reagan this fall than Bill Scott would have," said Fairfax Del. Lawrence Pratt, one of Reagan's more conservative Virginia backers.

Despite the unity theme that dominated the convention's conclusion today, there were subtle hints that the coexistence between mainstream Republicans and their more right-wing counterparts was an uneasy one.

A Norfolk delegate who appeared before a Northern Virginia causus this morning to boost conservative Illinois Rep. Philip Crane for vice president was booed repeatedly after suggesting Reagan needed a staunch right-wing running mate.

Emotions again nearly boiled over this afternoon when consrvatives presented a surprise resolution calling for Reagan to reject for the vice president nomination anyone who had supported the Panama Canal Treaty, a clear swipe at Tennessee Sen. Howard Baker.

The resolution was narrowly rejected on a voice vote after state Sen. Wiley F. Mitchell of Alexandria warned that "if the members of this convention wish to drive a wedge into the unity here today, you could no more do so than if you brought a mallet and a wedge in your hand."

Reagan did not put in an appearance here -- his staff said he had previous commitments -- but sent daughter Maureen Reagan and Rep. Jack Kemp of Buffalo, N.Y., another Republican figuring in vice-presidential speculation, to speak for him.

In the only major contest of the day, the convention by nearly a 2-to-1 margin elected Helen Obenshain as national committeewoman. Obenshain is the widow of the party's late 1978 senatorial candidate, Richard Obsenshain.