Aubrey Huff also homered for the Orioles, who snapped a five-game skid that began with an 8-0 loss at Yankee Stadium in which Olson yielded six runs before being yanked in the third inning. After waiting patiently, Olson (4-1) pitched a gem.
"You can always dwell on it, but that's not going to do you any good," the rookie said. "Every fifth day if you get the ball, you've got to go out there and get the job done."
Which is precisely what happened. Olson did not allow a hit after the third inning, matched his career high with seven strikeouts and walked four.
"It always comes down to location, and today, he had great location," Yankees manager Joe Girardi said. "He used his changeup a little more effectively today."
Chad Bradford worked a perfect eighth and Jamie Walker gave up a run and two hits in the ninth.
Olson outpitched Rasner, who gave up one run and five hits in six innings. Rasner (3-1) had won each of his three starts - including that 8-0 game against Baltimore - since being recalled from the minors on May 4.
Hideki Matsui had three of New York's five hits and scored the Yankees' lone run, on a ninth-inning single by Chad Moeller. Before Moeller's hit, New York was 1-for-8 with runners in scoring position.
"It happens," Girardi said. "They're not going to be perfect every time. There are good days and days that aren't your day. It's one game and you move on."
Markakis put Baltimore up 1-0 with his ninth homer on a 3-2 pitch from Rasner in the sixth, and added an RBI single in a five-run seventh against New York relievers LaTroy Hawkins and Jose Veras.
Earlier, Markakis broke an 0-for-13 slump with a third-inning double.
"Anytime you get a hit, it's a good feeling and it's a confidence builder," Markakis said. "I've been struggling the past couple weeks."
He got two hits against Rasner and is 9-for-11 with two doubles and a homer against the right-hander.
Markakis also made the defensive play of the game, a throw from right field that cut down Johnny Damon at home in the third inning.
"Him throwing that guy out at the plate was probably the key thing for us," Orioles manager Dave Trembley said.
"It always feels good to hit the ball out of the park, but it's not all about hitting," Markakis said. "You've got to play defense, too, and good teams play good defense."
The Orioles loaded the bases with two outs in the second before Rasner struck out Freddie Bynum on three pitches.
New York got a runner to second base in each of the first three innings but came away empty. In the third, Damon was thrown out by Markakis trying to score on a two-out single by Matsui.
"The way the pitchers were pitching early, it definitely was a big play in the game," Markakis said.
Said Damon: "He has a great arm. I felt pretty good running there, but he got me by a couple steps."
Markakis broke up the scoreless duel in the sixth with a drive to center that traveled an estimated 423 feet. In the seventh, Melvin Mora and Markakis had successive run-scoring singles with two outs before Huff hit his eighth home run, a three-run drive to right-center that was his second in two games.
