Quigley's third-round 6-under 66, the best of the tournament at Laurel Valley Golf Club, boosted him to 8 under. He was two shots ahead of Jerry Pate and Mike Reid.
But Quigley, who plays so many rounds of golf each year he rarely warms up before playing, tied Pate with a birdie on the dogleg par-4, 375-yard No. 15.
He followed with birdies on the water-guarded, par-3 No. 17, and the 515-yard, par-5 No. 18 while Pate was parring his final five holes.
``I hit a great 5-iron on 17 close ... and I had a pretty good heel print in my way and somehow the ball maneuvered around it and got in there,'' Quigley said. ``Eighteen, I hit just a terrible first putt and I thought it was really quick going down there. I left it 15 feet short and somehow slapped that one in. I was pretty much prepared to accept the three-putt on 18, but the ball went in so that's good stuff.''
The 58-year-old Quigley, a New Englander who lives in West Palm Beach, Fla., hasn't missed a senior tour event in seven years and has won more than $11 million on the tour after winning less than $100,000 on the PGA Tour.
Reid birdied No. 1 Saturday, parred each of the next 16 holes, then birdied No. 18 for his third consecutive 2-under 70 to join Pate at 6-under.
``I'm playing well - just sink a few putts,'' Pate said. ``If things go my way, I should be in good shape.''
Dave Barr and R.W. Eaks were four off the lead at 4-under, and 62-year-old Raymond Floyd and Peter Jacobsen were at 3-under. Morris Hatalsky was the only other golfer under par at 2 under.
Quigley's third round was the only one in the 60s - Laurel Valley was water-soaked and playing long after heavy rains Saturday morning - and only Reid and Hatalsky shot 70s.
Because the PGA was scrambling to complete the final round so a winner could be determined by the time NBC ended its afternoon telecast, the leaders had only about an hour's rest after finishing and starting the final round.
Last year's final round at Valhalla in Louisville, Ky., was delayed to Monday because of rain, but the PGA hoped a favorable forecast - only possible showers - would allow this year's first major on the Champions Tour to be concluded Sunday.
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