Scott McGregor spaced eight hits and Ken Singleton drove in four runs as the Baltimore Orioles defeated the Seattle Mariners, 9-1, tonight.

McGregor (3-0) pitched his third complete game in five starts. He struck out three, did not walk a batter and lost his shutout bid on Richie Zisk's sixth-inning homer.

Singleton's hit-and-run double off the left field wall with one out in the third scored Eddie Murray and John Lowenstein.

Dan Ford opened the third with a single. One out later, he stole second and went to third on Murray's single. Lowenstein singled Ford home and Singleton's double made it 3-0. Leo Hernandez's RBI single chased Jim Beattie (0-1).

Beattie, making his first start after being troubled by tendinitis, gave up nine hits in 2 2/3 innings.

The Orioles got five runs in the ninth against Roy Thomas and Ed Vande Berg. The first two scored when third baseman Dave Edler booted Cal Ripken's grounder with runners at second and third, allowing both to score. Singleton's single scored two and Rich Dauer had a sacrifice fly.

The Mariners bungled a first-inning chance. Zisk hit a line drive off the left field wall with one out and runners at first and second. Steve Henderson, the runner on second, headed back to the bag, thinking the ball would be caught.

After the ball bounced away from left fielder Lowenstein, Henderson headed for third. Dave Henderson, the runner on first, rounded second and started back toward the base, but hesitated when he saw Zisk nearing the bag and was run down. Steve Henderson wound up at third and Zisk at first. Todd Cruz flied out to end the inning.

Ripken failed to hit and his nine-game streak ended.

Seattle has lost 10 of its last 12 games. Mariner outfielder Al Cowens was attending the funeral of his brother-in-law, who was stabbed on a bus in Los Angeles.