Montreal played a man short for the final 20 minutes after Nelson Rivas picked up his second yellow card of the contest, but the Dynamo already had a 2-0 lead when he exited the game.
Houston will next take on New York in a two-game, aggregate-score series to determine one of the spots in the Eastern Conference finals. The first leg of that series will be played in Houston on Sunday with New York hosting the second game next Wednesday.
Bruin scored in the 17th minute and Oscar Boniek Garcia added a goal on a penalty kick in the 27th minute. Bruin's second goal came two minutes after Rivas was removed from the game.
Tally Hall made three saves to record the shutout.
The other Eastern Conference semifinal series will send New York against New England. In the Western Conference, it will be Portland vs. Seattle and Real Salt Lake vs. Los Angeles.