Among the notable early starters were world number two Phil Mickelson and three-times major winner Vijay Singh of Fiji, who began their rounds together 11 shots off the pace.
Tiger Woods, the only five-times winner on the PGA Tour this year, was three groups behind and has plenty of work to do if he plans to be in contention when the year's final major draws to a conclusion on Sunday.
Woods, who began his round 10 strokes behind leader Jason Dufner, has never won one of golf's elite championships when trailing after 54 holes and has failed to break par in six rounds of major championship play at Oak Hill.
The world number one arrived at Oak Hill as a heavy favourite to snap a five-year victory drought in the majors following a convincing win at last week's WGC-Bridgestone Invitational but has been a shadow of his dominant self.
Woods began the third round with a bogey at the par-four first where he missed the fairway badly to the left and was unable to reach the green in two.
Among the early starters, only 11 players were under par for the day, Zimbabwe's Brendon de Jonge making the biggest move with three birdies in his first four holes.
American Dufner, who reached the midway point of the year's final major with a two-shot lead, was scheduled to tee off at 2:55 p.m. (1855 GMT) alongside Australian Masters champion Adam Scott.
Dufner was among several players who took advantage of the rain-softened conditions in Friday's second round when heavy downpours gave way to sunny skies in the afternoon.
The 33-year-old double winner on the PGA Tour had a chance to shoot the first 62 at one of golf's four elite championships but left a 12-foot uphill putt 18 inches short of the cup on his final hole.
He tapped in for par to become the 24th player to shoot a 63 in a major and his two-day 131 total tied the 36-hole PGA Championship record.
Scott was two shots off the pace, along with Americans Matt Kuchar and Jim Furyk, while U.S. Open champion Justin Rose and Henrik Stenson were a further shot back at six-under 134.
American Webb Simpson, who also flirted with a record-tying 63 on Friday before settling for a six-under-par 64, will tee off at 2:15 p.m. with Germany's Martin Kaymer.
(Editing by Mark Lamport-Stokes)
