Keuchel yielded only one hit and struck out four across three shutout innings.
"You can't make many mistakes," Keuchel said about facing the Nationals. "They've got the reigning MVP; you've got Jayson Werth; you've got Ryan Zimmerman. Ben Revere starts it off… so it was good for me, my second start to face some good quality hitters and really focus on command and location."
Correa smashed his first home run of the spring in the first inning, a solo homer off Ross to give Houston an early lead. Ross held the Astros to the one run on five hits, walking two and striking out three.
In the fourth inning, Astros first baseman Tyler White tried to advance from first to third base on a single from Jon Singleton, but was thrown out from right field by Harper.
Ross got out of the inning shortly after to hold the Astros to the one run on five hits, walking two and striking out three.
"He was outstanding other than that home run," manager Dusty Baker said, "and he didn't give it up to a slouch. He was electric today. He threw easy gas and easy strikes. I like some Joe Ross."
The Nationals scored in the sixth inning when Reed Johnson got hit by a pitch from Astros reliever James Hoyt with the bases loaded to force in a run. But Washington left 13 runners on base and struck out 11 times -- especially late in the game -- leaving Baker frustrated.
"I was always told [the pitcher's] in trouble, not you," Baker said. "It's a matter of concentration. And desire. It's tough to watch sometimes. ... We have to change that big time."
Up next for the Astros: Collin McHugh makes his third start this spring when the Astros host the Nationals at 12:05 p.m. CT Tuesday at Osceola County Stadium on MLB.TV. In two previous spring starts, McHugh has not allowed a run over five innings.
Up next for the Nationals: Gio Gonzalez is scheduled to throw four innings in his third Grapefruit League start when the Nationals face the Astros at 1:05 p.m. ET on MLB.TV. Werth, Daniel Murphy and Danny Espinosa are all expected to be in the Nationals' starting lineup.
Jamal Collier is a reporter for MLB.com. Follow him on Twitter at @jamalcollier. This story was not subject to the approval of Major League Baseball or its clubs.