Nothing less than a sweep would do, and that's what they got.
Rodrigo Lopez pitched eight innings of four-hit ball, and Baltimore made it three in a row over Houston with a 5-1 victory Wednesday night.
Melvin Mora homered, Jay Gibbons had three hits and Brian Roberts went 2-for-3 with two RBI for the Orioles, who outscored Houston 19-7 in their first interleague sweep since July 1999, against Montreal.
Baltimore had lost four of five to conclude a 6-7 road swing before feasting on the Astros, who came to town with a five-game winning streak and a 7-23 record on the road.
"There are certain times when you obviously need to win, and this is one of those times," Roberts said. "We played OK on the road, and then when you get home you need to win, especially if you're playing teams that are kind of down and not really playing as well as they would like."
That pretty much describes the Astros, who got a home run from Jason Lane but did little else offensively in losing their sixth straight interleague road game. Houston has scored one run or fewer in 13 of its 33 road games, including the last two of this series.
"Once again we didn't get much going," said Houston's Craig Biggio, who went 2-for-12 in the sweep.
The Astros totaled eight hits in the final two games and never held the lead.
"The answer is to grind it out and get good at-bats," Houston manager Phil Garner said. "Let's have a good game and see what happens. Right now, I'd be happy with just one hit when we needed it. Just put the ball in play when we have men on base."
That's what happened in the first inning, but a stellar defensive play by Roberts at second base saved a run and enabled the Orioles to take control in the bottom half.
With runners at the corners and two outs, Roberts went deep in the hole to snare a grounder by Morgan Ensberg. While prone, he unleashed a throw to first that beat the runner.
"That play kind of set the tone," Baltimore manager Lee Mazzilli said.
Garner said, "Maybe if we had scored that run early, it would have come out differently."
The Orioles went up 2-0 when Roberts hit a leadoff single and Mora drove a fastball into the left-field seats for his 14th home run.
Baltimore used an infield hit, a hit batter and a walk to load the bases in the second inning for Roberts, who delivered a two-run single to make it 4-0.
"That's what we have to do, score early. Then Rodrigo can be more relaxed," Mora said.
Lopez (6-2) allowed one run, struck out seven and walked one in winning his fourth straight decision. He's 4-1 in 10 starts since April 21 -- the last day the Orioles were not in first place in the AL East.
It was the 19th time this season that a Baltimore starter went at least seven innings without giving up more than one earned run. Todd Williams worked the ninth to complete the four-hitter.
Rookie Wandy Rodriguez (2-3) gave up four runs in the first two innings, putting the Astros in a hole from which they could not recover. The left-hander ended up allowing four runs, seven hits and three walks in six innings.
Lopez retired 11 straight before Lane led off the fifth with his 10th home run on a 3-1 pitch. It was his second homer in the series and fifth in 11 games this month.
After Baltimore loaded the bases with no outs in the seventh against John Franco, Miguel Tejada hit a sacrifice fly off Dan Wheeler for a 5-1 lead.
Houston turned a season-high four double plays. The Astros ended the first three innings with 1-6-3 DPs, twice victimizing Rafael Palmeiro. ... Houston's Willy Taveras went 0-for-4 and was 1-for-14 in the series. ... Baltimore OF Napoleon Calzado, who was designated for assignment Monday, cleared waivers and was optioned to Triple-A Ottawa.