Baltimore Oriole first baseman Eddie Murray, one of baseball's top sluggers, has signed a multiyear, multimillion-dollar contract that will make him the highest-paid Oriole player, The Washington Post learned last night. h

Although he would not reveal the terms, Oriole owner Edward Bennett Williams confirmed that Murray signed the contract on Tuesday.

It was learned that the contract is for five years, with an option for a sixth year. The actual dollar figure is hard to determine, sources said, because of contingency clauses.The contract, according to one source, could be worth $1 million annually and, it was learned, does not contain a cost-of-living increase, as did the 10-year agreeement Dave Winfield recently signed with the New York Yankees.

It also was learned that the Orioles are in serious negotiations with free agent Juan Beniquez, who could fill their left field needs, and that they are close to signing outfielder Ken Singleton to a new contract. His current Baltimore contract expires after the 1981 season.

With Murray's signing, the Orioles now have retained veterans Jim Palmer, Scott McGregor, Rich Dauer, Doug DeCinces and Murray.

"Our top priority," Williams had said recently, "is to sign our present stars and go into the free-agent market only to fill our needs."

The Orioles have signed two free agents thus far: Jose Morales, who figures to play left field and pinch hit, and Jim Dwyer, an outfielder and first baseman.

In only four full seasons, the 24-year-old switch-hitting Murray has hit 111 home runs and driven in 398 runs. In 1977, he was the rookie of the year after hitting .283 with 27 home runs and 88 RBI. He increased his batting average every season, from .283 to .285 to .295 to .300 this past season. He led the team with 32 home runs and 116 RBI. He had 186 hits.

Murray's signing probably is the most important contract agreement of any Oriole player. Although his contract expired at the end of the 1980 season, Murray could not have become a free agent until 1982, after his sixth major league season, because of the players' collective bargaining agreement with the owners.

Murray, considered one of the best at his position in baseball, is looked upon by general managers as the Orioles' most valuable commodity, even more important to the team's success than Baltimore's three Cy Young Award winners -- Palmer, Mike Flanagan and Steve Stone.

His agreement to a lucrative contract demonstrates that the Orioles are capable of retaining their own key players, which many baseball insiders believed they could not do.

One such official said just last week, "The Orioles won't exist much longer, their farm system is bled," meaning that Baltimore would not be able to win 100 games a year unless they abandoned their frugal salary policies and signed the nucleus of their current team.

With Murray signed, William and General Manager Hank Peters should find it easier to sign Flanagan Dennis Martinez, Al Bumbrey and Tippy Martinez -- each of whose contract expires by the end of the 1982 season.

Several players hinted last season they might not be interested in staying in Baltimore if Murray and Singleton -- the Team's only true power hitters -- left the club. Murray, the cleanup hitter, is the team's most consistent player. He had played in 444 consecutive games before being sidelined with an eye injury for one game last season.

Murray also has more than 600 at-bats each season and has increased his number of hits each year.

If Baltimore can sign Beniquez, the journeyman outfielder would have a chance to be the team's starting left fielder.