Colsaerts had a first-round, 8-under 62 and is two strokes ahead of Kenneth Ferrie and Shiv Kapur, both of whom eagled the 18th hole and are tied at 6-under. Seven golfers are another stroke back at 5-under 65.
Colsaerts was three under after 12 holes before closing with five birdies in his final six holes.
That run started at the par-3 13th hole where Colsaerts had his tee shot end up 4 feet from the hole. His birdie at 14 came on a 7-foot putt. He finished the round with a two-putt birdie from 25 feet on the 499-yard, plar-5 18th hole.
"It's like a home tournament for me and I grew up playing very similar courses in Belgium so I feel very comfortable here in this course with the trees everywhere and a very traditional layout," Colsaerts said. "There have been some changes here and they have done them very well. I love these courses because I am so used to the layouts."