Cecil Cooper's three RBI and Robin Yount's four hits led the Milwaukee Brewers over the Boston Red Sox, 10-5, last night in a rain-interrupted game in Milwaukee.

The Brewers trail first-place Detroit by three points in the American League East. The Red Sox are 1 1/2 games behind Detroit and Milwaukee. The Brewer victory knocked the Baltimore Orioles from the race.

Yount led off the fifth with a single and moved to third when Cooper doubled. Gorman Thomas' single scored Yount. Ben Oglivie's double scored Thomas, and Sal Bando's single gave the Brewers an 8-3 lead.

Milwaukee scored two in the sixth on Cooper's RBI single and a sacrifice fly by Ted Simmons.

The Brewers scored on Cooper's first-inning sacrifice fly and Jim Gantner's second-inning sacrifice fly. Boston got three in the third on Dwight Evans' two-run double and Carney Lansford's single.

The Brewers tied the score at 3 in the third on Yount's triple and Cooper's ground out and took a 4-3 lead in the fourth, helped by Carl Yastrzemski's two errors.

Winner Randy Lerch (7-9) worked two scoreless relief innings.