Scott Fletcher's two-out double in the 12th inning scored Oddibe McDowell to give the Texas Rangers a 6-5 victory over the Baltimore Orioles tonight.

The loss was only the fourth in 13 games since the all-star break for the Orioles, but was a big one, because both teams in front of them were beaten.

McDowell started the winning rally with two outs by singling. Fletcher then doubled off the left-field wall to end the Orioles' five-game winning streak.

Reliever Greg Harris (5-8) got the victory and Odell Jones (1-1) the loss.

With the Boston Red Sox and New York Yankees both losing, the Orioles (55-45) missed a chance to move into second place within 3 1/2 games of first place in the American League East.

The final rally finished a crazy night. Lee Lacy's ninth homer gave the Orioles a 2-0 lead in the sixth, but the Rangers came back for a 5-2 lead in the last of the inning.

The Orioles closed it to 5-4 in the seventh when Juan Beniquez hit a two-run homer. The Rangers took that lead into the ninth, but the Orioles tied it.

The ninth began with a couple of pinch singles, one by John Shelby and another by rookie Tom Dodd, both off rookie reliever Mitch Williams.

Texas Manager Bobby Valentine went for his No. 1 short man, Harris, who struck out Beniquez but walked Tom O'Malley to put the tying run on third. Pinch hitter Jim Dwyer got that run home with a fly to center.

The Rangers missed a chance to win it in the 10th when Toby Harrah singled and McDowell walked with none out. Fletcher, trying to sacrifice, popped out. Ruben Sierra flied out to left and Pete Incaviglia grounded out to end the inning.

Texas' Mike Loynd, making his second major league start, allowed four runs and seven hits in six-plus innings and had a shutout until Lacy's home run.

The Orioles' Mike Flanagan had a shutout for five innings, but in the sixth the first four Rangers got hits, which is when Manager Earl Weaver went for Rich Bordi. He was outstanding, allowing three hits and a run in five innings.

The teams totaled only six hits the first five innings. The Orioles had three singles and got one runner as far as second, Larry Sheets, who singled and stole second in the fifth.

The Rangers also had three hits, but one of them was Larry Parrish's one-out double in the second. He went to second on Tom Paciorek's fly, but Flanagan got Don Slaught on a fly to center to end the inning.

Then came the sixth. Loynd gave Rick Dempsey a leadoff walk, and trying to get something going against Loynd's slow breaking pitches, Dempsey stole second. Juan Bonilla flied to left, but Lacy homered.

The lead didn't last long because the Rangers sent nine men to the plate, scoring five runs on six hits to take a 5-2 lead after two innings.

Flanagan faced only four hitters and got none of them him. Harrah and McDowell singled with none out and Fletcher blooped a single in front of center fielder Fred Lynn to score Harrah.

After Sierra singled to right to tie the game, Weaver called for Bordi, who promptly cost Flanagan two more runs. Incaviglia's double off Bordi scored Fletcher for a 3-2 lead. The Orioles then brought the infield in for a play at the plate, and Parrish grounded a single past that defense to score two runs. That made it 5-2, but Bordi retired three in a row to end the sixth.

The Orioles bounced back to get two more in the seventh when Sheets led off with a single and Beniquez homered to left, his second in as many nights.

Valentine brought in reliever Dale Mohorcic, a 30-year-old rookie, who got out of the seventh with a 5-4 lead.

Not that the Orioles should been totally unfamiliar with Loynd. They picked him in the 11th round of the 1985 June draft, but couldn't sign him . . . It now appears first baseman Eddie Murray won't come off the disabled list until late next week, at the earliest. Doctors have asked him not to take batting practice until the Orioles return to Memorial Stadium.

With 21 homers in 13 games since the break, the Orioles have now hit 106 and have moved from 10th to fifth in the American League home-run rankings . . . They are on a pace to hit 172. However, they're still 12th in the other power category, doubles.