It was Beltre's only hit of the contest.
Jose Lopez had a run and two of the six hits for the Mariners (53-54). Seattle, fighting for at least a wild-card berth in the American League, has won four of its last five games.
Jay Gibbons hit a run-scoring single in the sixth inning. Five others had one hit for the Orioles (49-60), who have split their last four games.
Losing pitcher Erik Bedard (12-7) gave up two runs and four hits in 5 1/3 innings with three walks and five strikeouts.
Couple mistakenly served bag of cash at McDonald's drive-thru
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'