Former winner Hale Irwin posted a 4-under 68 to share fourth place with Peter Jacobsen and Ron Streck. Bruce Fleisher and Dick Mast followed at 7-under-par 137.
Quigley hit a wedge inside 5 feet for a birdie at the par-4 sixth, his only birdie on the front nine. The back nine was a different story, however, and Quigley ran off the first of three consecutive birdies at the 10th after his second shot stopped 16 feet from the cup.
'The day was pretty exceptional,' he said. 'I hit the ball extremely well.'
The 58-year-old, who tied for second at this event in 2000, played his approach to 18 feet for a birdie at the par-4 14th. Quigley added a birdie at the par-4 16th to reach 11 under and take the lead in the clubhouse in time to avoid a lengthy delay.
Dangerous weather approached the TPC of Michigan in the afternoon, stopping the second round for over three hours. The players ultimately returned to the course at 4:50 p.m. (et) to resume action.
Quigley began his streak of consecutive tournaments played in 1997, but a hip injury might force him to skip the Senior British Open. With that possibility on the horizon, Quigley has carried on as he always has this week.
'It hasn't affected my golf whatsoever,' said Quigley. 'It's not comfortable to sit on yet by any means. That's really going to be my determining factor where I go to Scotland, is whether I can sit in the plane for seven hours.'
Aoki got his round in before the delay. He tallied a bogey and a pair of birdies over his first nine holes to make the turn at 7 under. Aoki drained a 9-foot putt for a birdie at the par-3 12th and rolled in a long birdie putt at the 14th en route to a round of 69.
'I putted well today,' Aoki said. 'We were in the first group and we had no wind and good conditions.'
McKnight was on fire on the front nine with five birdies to climb to 9 under around the turn. He suffered a double bogey at the par-4 10th, but came back with a birdie at the par-3 12th after his tee ball landed 7 feet from the hole.
He picked up another birdie at the par-3 15th and parred his way in for a 67.
'I hit a lot of good iron shots the last couple of days,' said McKnight. 'I'm playing well.'
Irwin collected three birdies on the front nine and drained a 10-footer for a birdie at the 13th to finish three shots back.
'I lost momentum with the delay,' said Irwin. 'Never quite got the feel again. Two rounds left to go, but I'm very happy with my position.'
Tom Watson managed an even-par 72 to fall back into a tie for ninth place. He was joined by Morris Hatalsky, Jim Ahern, Gil Morgan, Jerry Pate and John Harris at 6-under-par 138.
Defending champion Mark James was one shot further back in a group at 5-under-par 139 after a round of 69.