Overton, looking for his first PGA Tour win, finished 54 holes at 18-under 192, leading D.A. Points (61) by three shots at minus-15 and third-place Boo Weekley (67) by five at minus-13.
The main attraction Saturday at The Old White Course, however, came as both Points and J.B. Holmes flirted with 59s.
Points needed just one more birdie to shoot a 59 after going 10-under through his first 16 holes. But he three-putted for bogey at the 17th and made a routine par at the 18th to fall two strokes short.
Holmes, meanwhile, finished with a 60 after missing a 4-foot birdie putt at No. 11 and a 10-footer for eagle at No. 17.
Holmes ended up sharing fourth place with Jonathan Byrd (64), Brendon de Jonge (65) and Jimmy Walker (67).
Exploding whale video goes viral on Internet
Wisconsin business offering 'therapeutic cuddling' forced to close