The victory leaves the Sounders with an 8-8-4 record, while Houston fell to 5-9-5.
After a scoreless first half, Montero gathered in a long ball from goalkeeper Kasey Keller, shielded it from defender Eddie Robinson and fired it past Dynamo goalkeeper Tally Hall in the 64th minute. It was Montero's eighth score this season.
Montero then assisted on the Sounders' second goal in the closing minutes when he got the ball to Alvaro Fernandez, who knocked it home just inside the right post for his first Major League Soccer goal.
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