BALTIMORE -- Jason Castro hit a grand slam while Matt Dominguez and Robbie Grossman also homered to help back up the solid pitching of Brett Oberholtzer as the Houston Astros rolled to an 11-0 victory over the Baltimore Orioles Wednesday night at Camden Yards.
Castro's first career grand slam broke the game open as part of a five-run fourth which gave Houston (36-70) a 9-0 lead. He finished 3-for-4 with those four RBIs.
Dominguez hit a solo homer in the seventh as part of his 4-for-5 night with two RBIs as he had a run-scoring single earlier. Grossman (2-for-4, two RBIs) added a two-run homer as part of a four-run third, and that was his first major league homer.
The power display helped Brett Oberholtzer (1-0) earn his first major league victory in his first major league start-after three relief appearances.
Former Oriole Erik Bedard had been the scheduled starter, but the Astros scratched him earlier in the day and called on Oberholtzer. The left-hander threw seven shutout innings. He allowed only three hits while striking out six and walking none, keeping the Orioles (59-49) off-balance all night.
Adding to the night of firsts for Houston, right-hander Chia-Jen Lo made his major league debut when he replaced Oberholtzer in the eighth.
Baltimore finished with seven hits, five of which came in the last three innings, but the Orioles couldn't score.
The Orioles and Astros completed a trade before the game. Baltimore acquired starting pitcher Bud Norris from Houston in exchange for outfielder L.J. Hoes and minor-league pitcher Josh Hader.
Norris had been scheduled to start Monday night's series opener, but was scratched. In addition, Hoes was originally in Baltimore's starting lineup for this game but went over to the Astros and joined their lineup, batting second and playing right field.
For the second straight night, Houston took an early lead. This time, the Astros scored four runs in the second inning against Orioles starter Miguel Gonzalez (8-5).
Brandon Barnes drove in the first run with a two-out RBI double. Matt Dominguez followed with an RBI single up the middle, and Robbie Grossman then blasted a two-run homer inside the right-field foul pole, his first major-league homer.
But unlike Tuesday, the Astros took control after that. They broke it open with a five-run fourth inning for a 9-0 lead.
Gonzalez nearly got out of the inning unscathed, but shortstop J.J. Hardy booted Jose Altuve's two-out grounder that would have ended the fourth.
NOTES: Manny Machado (third base) and Hardy (shortstop) have started 148 consecutive games together on the left side since Aug. 21, 2012. STATS says that's the longest such streak in the majors in 60 years. ... Jim Johnson now has 108 career saves, which ranks second in Orioles club history, behind only Gregg Olson (160). ... The Astros now have scratched their original starters in each of the first two games of this series. ... This victory was Houston's first in Baltimore. The Astros came into this game with an 0-7 record at Camden Yards.