Piercy closest competitor was Will Wilcox, who hit a final-round 67, while Robby Shelton, Whee Kim and Ricky Barnes finished five shots behind Piercy in a tie for third.
Piercy made eight birdies and two bogeys in his round of 65 to finish on 19-under for the tournament. His most impressive moment of the day came at the second where he sunk a 57-foot birdie putt.
Wilcox went one by better by converting an incredible 60-foot birdie putt at the 18th, and despite recording five birdies and just a single bogey, he still finished three strokes behind his American compatriot.
Shelton, Kim and Barnes finished with rounds of 67, 69 and 70 respectively, while Andrew Loupe, Boo Weekley, Austin Cook and Mark Hensby finished in a tie for sixth.