The Canadiens kept the Capitals winless in the young season. Washington went into the evening as one of four NHL teams without a point.
After a scoreless opening 20 minutes, Plekanec tallied 3:47 into the second and Markov followed 57 seconds later.
Price had his shutout bid spoiled by Joey Crabb with 2:33 to play, but made 30 saves to give Montreal back-to-back victories.
Michal Neuvirth allowed all four Montreal goals on 22 shots.