Monty said: "To come off any win is fabulous, but it is no good if you don't follow it up. That is why I'm pleased with this round. Right now my game is as good as it's been for quite some time."
Also in with a 68 was Argentine Gustavo Rojas, but out on the course was Scot Andrew Coltart, who birdied his first four holes.
They are all just one shot off the five-under-par total posted in the clubhouse by Italy's Massimo Scarpa, Henrik Bjornstad of Norway and Australian Brett Rumford.
US Open champion Retief Goosen of South Africa is two under four with playing partner Lee Westwood level par.