Mike Flanagan pitched a six-hit shutout tonight and Ken Singleton slammed his 17th home run of the season as the Baltimore Orioles completed their best month in the club's 26 years.

The 2-0 victory over the cellar-dwelling Toronto Blue Jays brought the American League East leaders' June record to 23-6, the .794 winning percentage being the best in the history of the franchise.

The Orioles did little wrong during the month.

The statring pitchers, for the most part, shut down the opposition. The bullpen notched a 9-0 mark with seven through with late-game heroics. The substitutes contributed valuable offensive and defensive efforts. And the Orioles, except for one day, led the Al East since May 18.

"if we play the same way in July, I hope we have more of a lead than 4 1/2 games over Boston by August," said Manager Earl Weaver. "All this month meant was that we put an awful lot of numbers in the win column that somebody's getting less and less time to make up."

Following Sunday afternoon's conclusion of the four-game Blue Jay series, the Orioles embark on a two week trip that pits them against West Division powers Texas and California among others.

Flanagan walked only one Blue Jay and struck out three to become the league's third 10-game winner. He has lost five. It was his third straight victory, second shutout and sixth complete game.

No Blue Jay reached third base and only two got to second as Toronto never seriously threatned to add to the one run it has scored in three games.

"our bullpen is getting so good that the starters had to come out and do something about it," said Flanagan, 19-15 last season. Flanagan held Toronto's four best hitters -- Rico Carty, John Gomex -- to a collective one-for-15.

Singleton got the Birds on the board early with his two-out 380-foot blast over the left-field fence. That was the switch hitter's fourth homer right-handed. He nearly launched another in the eighth, but center fielder Rick Rosetti made the catch two feet in front of the 400-foot mark.

A throwing error by catcher Rick Cerone provided Baltimore's other run. Doug DeCinces led off the sixth with a walk off starter Tom Underwood and reached second on a wild pitch. One out later, Gary Roenicke singled DeCinces to third and stole second on Underwood's next pitch. Cerone's throw to second attempting to nab Roenicke bounced into the outfield.

Cerone and Ainge put minimal pressure on Flanagan's shutout bid with two-out singles in the seventh, but Flanagan escaped by getting Bob Bailor to pop up.

The last Blue Jay to reach base, eighth-inning leadoff batter Alfredo Griffin, was naileld by a fine pickoff throw from Flanagan to first baseman Eddie Murray.

Once again, the appreciative crowd of 19,807 -- which had braved threats of electrical storms to watch the Orioles increase their home mark to 30-9 for the year -- refused to leave until the latest pitching hero stepped out of the dugout for the obligatory postgame doffing of his cap.

The only area natives not entirely pleased were the concessionaires, who have had only an average of 2 hours 9 minutes to sell their wares during the Toronto series. CAPTION: Picture, Yankee pitcher Luis Tiant throws out Boston's Jerry Remy. AP