The hosts started brightly and almost went ahead after 15 minutes when Justin Mapp found space on the edge of the box, but his curling effort bounced wide off the post.
Mapp was involved again shortly after, finding Marco Di Vaio in space in the box, before the former Parma striker smashed the ball into the top corner to give Montreal the lead.
They doubled the lead two minutes later, with Mapp again the provider. This time his cross found Felipe Martins, who curled the ball into the far corner.
Houston improved after the break, but it was Montreal that scored again thanks to Jeb Brovsky, who reacted quickest to tap in following a corner.
Di Vaio then got his second of the game, collecting a clever through-ball and finishing well from the middle of the area.
There was still time to add a fifth, as Andrea Pisanu curled his effort into the corner with the final kick of the game.