The offense showed some unusual power with two-run homers from Matt LaPorta -- his first of the season -- and Russell Branyan. LaPorta's shot gave Westbrook a 3-0 lead in the fifth, and he took charge from there as the Indians won a second straight game.
"It was a very good outing by him to give him a big-time boost in his confidence after being out for so long," said Cleveland manager Manny Acta.
Westbook (2-2) said giving up the solo homer to Luke Scott with two outs in the bottom of the ninth to lose the shutout was a little discouraging, but the right-hander really wanted to finish the job.
"It was good to get a complete game," Westbook said. "It was good to get a 'W.' I feel great right now, and that's encouraging to me. It just gives you a little bit of peace where you don't have to worry about your arm."
Westbrook has been improving throughout this season. He's thrown effectively in three of his last four starts, and his ERA fell to 4.27 with this performance.
The right-hander had good movement on his sinker, and free-swinging Baltimore (12-26) kept pounding balls into the ground.
"Westbrook had tremendous movement on his ball today," said Baltimore's Ty Wigginton." He mixed in enough sliders, so if you went to get on the sinker, the ball is diving away. You get a lot of bad swings when a guy has a good sinker working. He was outstanding."
The Orioles caused a number of problems early for Westbrook, who said he got stronger as the game went on. Baltimore got two hits in the first, second and fourth innings and had hits in five of the first six frames.
But Westbrook got some help in the first, when center fielder Grady Sizemore made a diving catch of a Wigginton liner in right-center with two on and two outs to save at least one run.
The Orioles put runners on second and third with two outs in the second before Westbrook struck out Corey Patterson. Shin-Soo Choo gunned down Wigginton at second as the Orioles second baseman tried to stretch a single into a double in the fourth.
Cleveland (15-20) also turned double plays to end the fourth and fifth. Both Westbrook and Acta said the defense was a big reason for the complete game and the victory.
"We need to do that for us to have any type of success because we don't have that many strikeout pitchers on our staff," Acta said. "That's something we have improved a lot. We played very good defense so far."
The Indians took a 1-0 lead when Sizemore got an RBI single in the third to drive in Lou Marson, who had singled. Sizemore came out in the fifth with a left knee contusion, and he's day-to-day.
Cleveland made it 3-0 when LaPorta hit a two-run homer to deep center off Baltimore starter Mark Hendrickson (1-1), who was pressed into emergency service when scheduled starter David Hernandez was scratched due to shoulder discomfort.
Branyan's two-run shot in the ninth off Alberto Castillo gave the Indians a 5-0 lead.
Acta said they can't really say that Westbrook is all the way back. But the Indians are pleased with his stamina and velocity, and they're hopeful that he can keep pitching effectively and look more like he did in years past.
"It was nice to get into the seventh and eighth," Westbrook said. "It was good to get a complete game. I felt good. I felt real good."