Youngster Gyasi Zardes impressed with a goal and an assist in the absence of Landon Donovan and Omar Gonzalez.
The Galaxy took the lead in the 24th minute through Robbie Keane. The Irishman took Gyasi Zardes' cross-field square ball, cut inside past two defenders, and struck from 20 yards to beat Raul Fernandez.
Zardes grabbed one for himself just before haltime. Juninho's inswinging cross fell just behind the Dallas back line, and Zardes snuck in to head home from six yards and double his team's lead.
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Dallas got on the board in the 65th minute. Jair Benitez snuffed out a Galaxy move out of defense and curled a perfect cross the the perhaps-slightly-offside Tesho Akindele, who turned the ball past Jaime Penedo.
The Galaxy's win ends a four-game winless streak and moves them up to sixth in the Western Conference with a 3-3-3 record. Dallas is in third with 5-6-2, but has played more matches than any other Western Conference side. It won't get much easier for the Hoops, which have a short turnaround before an away game against undefeated second-place Real Salt Lake on Saturday.