NEW YORK, JUNE 3 -- The Orioles, last in the American League in hitting, made several roster moves tonight on the eve of their series with the AL East-leading Milwaukee Brewers, whom they trail by 3 1/2 games.

Designated for assignment to one of the Orioles' farm teams was designated hitter-first baseman Sam Horn. Middle-relief pitcher Mickey Weston was sent to Class AAA Rochester.

To replace them on the roster, the Orioles called up catcher Chris Hoiles, the International League's leading hitter, and veteran first baseman Greg Walker.

"Obviously, these moves are being made to get some offense," Orioles spokesman Rick Vaughn said after the moves were made late tonight. "When you're last in the league in hitting, you've got to do something to enliven it.

"We're making a move here {in the standings}. You hate to get close and not be able to move because you're not getting any runs."

The Orioles hoped that Horn would be their everyday cleanup hitter, especially after he had two home runs and six RBI on opening day. But he had only one homer and six RBI since and is batting .253.

Horn may become a free agent if he does not want to accept the Orioles' assignment, to be made in the next 10 days.

Hoiles is batting .394 and been above .400 for much of the spring, Vaughn said. He has 10 home runs and 31 RBI.

The Orioles indicated Hoiles, a right-hander, will platoon as a catcher and designated hitter with Mickey Tettleton.

Walker, 30, was picked up by the Orioles after the Chicago White Sox released him early in the season. He has a .262 career average in eight seasons and was the starting first baseman for the White Sox' 1983 AL West champions. In 1984, Walker hit .294 with 24 home runs and 75 RBI, but fell to .210 in 77 games last season.

He batted .303 with two homers and 11 RBI in 22 games this spring with Rochester.Ripken Plays in 1,300th

Shortstop Cal Ripken, whose consecutive-game streak began May 30, 1982, is eight games from surpassing Everett Scott as holder of the second-longest streak in major league history. Scott, also a shortstop, played 1,307 games from June 20, 1916, to Oct. 2, 1921. He began the streak while playing for the Boston Red Sox and ended it as a member of the Yankees.

The Yankees' Lou Gehrig holds the all-time record, 2,130 games.

Ripken has started all 1,300 games and played 12,828 of a possible 12,866 innings. He has played the entire game all but 11 times, with three of those in the last 11 days.

"It's a combination of a lot of things," Ripken said. "The desire to go out and play, a lot of luck and fielding a position that allows you to play every day."

His desire to play could be hereditary. "To me," said third-base coach Cal Ripken Sr., "the idea is to come to the ballpark ready to play a ballgame. That's the way I was, so that's the way my regular guys should be."

Although Ripken is batting .216, he is fielding almost flawlessly. He extended an errorless streak to 47 games today, matching the longest one of his career. He has one error this season and leads AL shortstops with a fielding percentage of .995.Tibbs Returns to Team

Pitcher Jay Tibbs, whose father died Wednesday, is scheduled to rejoin the Orioles tonight in Milwaukee, where they will begin a four-game series with the first-place Brewers on Monday night.

Tibbs's normal turn in the starting rotation is Tuesday night, but the Orioles said they are undecided about who will start that night. Pitching coach Al Jackson said today it is "possible" Jeff Ballard will start Tuesday.