Lee May belted a two-run homer in the fourth inning, and the Baltimore Orioles added four unearned runs in the eighth to beat the Toronto Blue Jays, 6-5, in the first game of a doubleheader tonight.

Ken Singleton opened the Orioles' fourth with a single and came home when May drilled a pitch off loser Jesse Jefferson into the left centerfield seats for his 23rd homer of the season.

Baltimore parlayed a pair of singles, two walks and errors by left fielder Al Woods and first baseman Doug Ault into a four-run eighth inning.

Mike Flanagan got the victory but needed eighth-inning relief help from Dick Drago, Tippy Martinez and Scott McGregor as the Blue Jays struck for four runs on RBI singles by Gary Woods and Rick Cerone, a base loaded walk to Steve Staggs and a sacrifice fly by pinch-hitter Doug Rader.

Flanagan struck out three and walked three in boosting his record to 12-10. The victory was his 10th in the last 12 decisions. Loser Jesse Jefferson gave up only five hits but was tagged for the four unearned runs.

Baltimore was held hitless for 3 1/3 innings before Singleton and May touched off the scoring.