Quigley stands at 12-under-par 132 for a one-stroke advantage over Loren Roberts, who shot a 65 in his second round to reach minus-11.
Jim Ahern (66), Jay Haas (67) and Tom McKnight (68) share third place at 9 under, while Brad Bryant (67) and Lonnie Nielsen (70) are one stroke further back in a tie for sixth.
The first round was completed Saturday morning following a weather suspension Friday night, and Quigley entered the second round tied for sixth place at 4 under.
He began his bogey-free round with two straight pars, but went on to birdie eight of the next 12 holes to climb the leaderboard at Rock Barn Golf Club.
Quigley made putts when he had to, despite soft conditions caused by heavy rains Friday. His eight birdies included a 70-foot putt at the par-3 third, a 15-footer at the seventh after escaping a bunker and a 17-footer at the 11th.
The 58-year-old has now gone 30 holes without a bogey since dropping a shot at the par-4 sixth on Friday. Part of the reason has been his good iron play -- he hit 17 greens in regulation -- but it was his work with the flat stick that produced the red numbers.
The 10-time Champions Tour winner -- who owns two titles this year already -- was happy with the course conditions after Friday's bad weather, although it forced the players to put a little extra on their putts.
'I think the biggest concern for all of us on these greens is getting the ball to the hole,' acknowledged Quigley, who leads the tour in Charles Schwab Cup points. 'You really got to hit it.'
Quigley has definitely made his case for Player of the Year honors, but those end-of-year type things aren't really on his mind heading into the final round.
'I just need to get that stuff out of my mind,' he said, before adding how much it would mean to win both Player of the Year and the Schwab Cup title.
Roberts was a casualty of the slow greens at 18, where he could have used a few more rolls on a birdie putt that would have given him a share of the lead.
The 5-foot try came up short and right, and Roberts ended his bogey-free round with four consecutive pars to assure himself a spot in the final group Sunday.
'I left some out there,' said Roberts, a Champions Tour rookie who picked up his maiden victory on the circuit at the JELD-WEN Tradition in August. 'We'll see what happens on Sunday.'
First-round leader Wayne Levi managed just an even-par 72 in his second round and fell into a tie for eighth place at 7 under. He was joined there by John Bland (68), Craig Stadler (67) and Tom Wargo (66).
Defending champion Doug Tewell is too far behind to be a repeat threat. He shot a 72 in his second round and is tied for 31st place at minus-2.