General Manger Bobby Beathard, who had predicted the Washington Redskins could make some major deals during yesterday's opening session of the National Football League draft, engineered two dramatic trades, the first with Baltimore for halfback Joe Washington, while selecting offensive tackle Mark May of Pittsburgh with his first-round choice.

By the time Beathard had finished wheeling and dealing -- he made one smaller trade late in the day -- the Redskins had:

May, the 6-foot-6, 265-pound Outland Trophy winner who is favored to beat out veteran Terry Hermeling; the elusive Washington, who provides the Redskins with the breakaway running threat they have lacked since giving up Mike Thomas; Russ Grimm, a 6-3 250-pound center from Pittsburgh who is projected to become the starting center; Tom Flick, a 6-2, 185-pound quarterback from the University of Washington who is expected to make Mike Kruczek expendable as Joe Theismann's backup; a fifth-round draft selection this year and a second-round choice next year, both from the Rams.

But to rework a major part of the offensive line and to add speed to the backfield, Beathard had to yield his No. 1 pick in 1982 and his second choice this year.

This is how the day unfolded:

To obtain Washington, who had been unhappy playing behind Curtis Dickey in Baltimore, the Redskins surrendered their No. 2 pick in this year's draft which they had obtained in a deal with the Rams two weeks ago. Talks with the Colts, begun two months ago, were completed 30 minutes before the draft began.

Beathard then selected May, rated by the Redskins as the ninth-best player in the draft, on the 20th turn in the first round. Beathard had been so pessimistic that a player of May's caliber still would be available when the Redskin's turn came that early yesterday he considered trading his No. 1 choice for two second-round picks.

To get Grimm, rated the 20th best player in the draft by the Redskins, Beathard first sent his No. 1 pick in 1982 to the Rams for a third-round pick and two fifth-round choices this year and a second-round selection next year. He used the third-round pick on Grimm, who had been downgraded by the scouting combines. Beathard, at one time, had decided to draft Grimm in the first round before changing his mind.

The Redskins switched places in the fourth round with Green Bay so they could pick Flick, rated by Coach Joe Gibbs ahead of the more publicized Neil Lomax. In addition, Washington gave Green Bay one of the fifth-round choices it had obtained from the Rams. After getting Flick, the Redskins lost interest in Miami's Don Strock, who had been offered a contract last week.

"This is the best draft I've been associated with," said Beathard, who defended giving up the 1982 first-round selection by predicting Grimm would become the starting center. "We're getting a No. 1 draft choice this year (Grimm) for a No. 1 next year. I don't consider it a gamble. There are two good defensive linemen in next year's draft, but we don't plan to go 6-10 again, so they wouldn't be there when we drafted.

"We've been after a quick halfback for two years and Washington is sensational. And May is going to be a star in this league for a long, long time. We've got a fine center prospect, the best around that we've seen for years. And we really think a lot of Tom Flick. We had him rated as the second-best quarterback in the draft."

Owner Jack Kent Cooke, who approved sending the No. 1 choice to Los Angeles and who was taking all day with Redskin Park, said he was "quietly confident about the outcome of this draft. I believe that this maybe is one of the better drafts the Redskins have had in years."

Before celebrating the deal for Washington, however, Beathard first must sign the running back to a new contract. Washington, who is entering the option year of his current contract, said yesterday that negotiating problems with the Colts had accelerated his desire to be traded. "We'll sign him," Beathard said.

When the draft was halted after six rounds, the Redskins also had selected, in the fifth round, defensive and Dexter Manley of Oklahoma State, who Beathard compares to a young Coy Bacon as a pass rusher, and guard Gary Sayre of Cameron (Okla.) State, who began his college career at Texas. In the sixth, they took linebacker Larry Kubin of Penn State, who missed last year with a knee injury. Kubin has announced he will play another year at Penn State, but the Redskins have until next year's draft to sign him.

It is apparent both Beathard and Gibbs are not about to undergo a patient rebuilding program. Beathard is enough of a scrambler to believe he can regain next year's first-round pick before that draft.

But the deals also put pressure on Beathard's talent-judging ability. Much as when he took Mat Mendenhall as a surprise No. 2 choice last year, he again has gone against the grain by selecting Grimm and Flick.

Gibbs' high-powered passing offense should benefit immensely from this draft. May's strength is pass blocking -- he allowed only one sack the last 2 1/2 years -- while Washington, once a first-round selection out of Oklahoma, has both the speed to make long gains (he ran for 956 and 884 yards his first two years with Baltimore) and the hands to be a dangerous receiver (he caught 82 passes in 1979 to lead the NFL).

The draft also should have a major impact on the starting offensive unit. With Washington as the No. 1 halfback, Wilbur Jackson can return to fullback and Clarence Harmon is free to become a third-down back, where he is most valuable.The line should have three new starters: May in place of Hermeling, Grimm in place of either Bob Kuziel or Dan Peiffer, and Fred Dean, who will shift from tackle to guard, where he most likely will replace veteran Ron Saul.

Beathard first revealed an interest in Washington, a 5-10, 185-pound six-year pro, after the NFL meetings in March. At that time, he said, the Colts' asking price, a high second-round selection, which the Redskins didn't then have, plus other considerations, was too steep.

He became even more pessimistic nine days ago after visiting with Colt Coach Mike McCormack at the Baltimore Offices. McCormack still insisted on an early second-round pick, and not the selection the Redskins had obtained in a trade with Los Angeles.

"I came back here and told everyone that the deal was off," Beathard said. "They had mentioned maybe a seond and a fifth, but that was also too much." Then Washington failed to show up for the Colt minicamp and he kept demanding to be traded instead of sharing time with Dickey. The Colts, who said five other teams were interested in Washington, called Beathard again Monday and the bargaining resumed.

Washington, a swift runner who has played full time only two of his five years in the league (an injured knee kept him from playing as a rookie), said, "I've seen the type of things Gibbs' offense does, lots of draws and quick traps, things I enjoy. He believes in moving downfield in big chunks. I run, catch and block. I do more blocking than most people realize."

Once Beathard had dealt off his second-round choice, he did not think he had a chance at Grimm, although he continued talking during the morning with the Rams, who had several extra choices. Grimm was rated by some experts as the fourth-best center in the draft, but Beathard and Joe Bugel, his line coach, thought the Pittsburgh star had the versatility (he can play guard, tackle and snap on kicks) and techniques to be a standout.

Gibbs worked out Flick and Lomax last week, and felt Flick, who guided Washington into the Rose Bowl this year, was superior. He and Beathard were convinced that, as Beathard put it, "we had problems (behind Theismann) at quarterback. If Joe got hurt, we weren't sure if we were good enough to replace him."

Beathard thought he had engineered a major trade two hours before the drafting started. He had reached tentative contract terms with Howard Slusher, agent for linebacker Bob Brudzinski, who had quit the Rams midway through last season in a contract dispute. But Beathard couldn't get in touch with anyone from Los Angeles to complete the deal. Meanwhile, he was called by Miami Coach Don Shula.

"I mentioned Brudzinski to him and Don said, 'Hey, we got him in a trade with the Rams last night.' I couldn't believe it," Beathard said. "But at least we managed to get Joe Washington later."