After Chivas USA's Eric Avila negated Barnes' early first goal with a score in the 50th minute, the Dynamo took command.
Barnes made it 2-1 in the 54th minute and Will Bruin put another shot past Chivas goalkeeper Dan Kennedy 10 minutes later for a 3-1 Houston advantage.
Garcia notched his first goal of the season 11 minutes from time and added a second goal in stoppage time for the final four-goal margin.
The Dynamo improved their hold on a playoff position with 43 points on the season.
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