Butch Sheehan, Dick Mast and Jay Sigel share fifth place at minus-four.
High winds and cold temperatures plagued the Coyote Creek Golf Club on Friday as players bundled into sweaters and wool hats.
Quigley picked up three birdies on his front nine but it was his run at the end of his round that put him in a tie for the lead. He landed in a greenside bunker in two at the par-5 17th but blasted out to 10 feet to set up birdie. He ran home a 15-footer for birdie at the last to get into the group at five-under par.
'I had a pretty good round today,' said Quigley. 'It was a nice surprise and to get a good round in early is good.'
Wargo played his round similar to Quigley's. He stood 3-under-par with four birdies and a bogey as he went to No. 17. Wargo birdied the 17th and 18th for his 5-under 67.
'I kept it in the fairway all day and that was the key for me because the rough is up here,' said Wargo, who hit every fairway on Friday. 'If you keep it in the fairways, you've got some shots. The greens are holding so you can take advantage of it.'
Gilder, last year's Senior Tour Rookie of the Year, fired out of the gates with four birdies in a row but ran into trouble with bogeys at five and seven. He added three more birdies on his front side for a total of seven on the opening nine, where he did not record a single par.
Gilder was even the rest of the way with a pair of birdies and a pair of bogeys.
Rachels was alone in first at 6-under par but dropped a shot at the par-5 17th to fall into the tie at the top of the leaderboard.
Rodger Davis, Tom Purtzer, Tom Jenkins, John Jacobs, John Mahaffey, John Schroeder and Andy North share eighth place at 4-under-par 69.
Defending champion Hale Irwin shot a 2-under 70 on Friday and shares 15th with a group that includes Fuzzy Zoeller and Lanny Wadkins.
Full-field scores from the Siebel Classic at Silicon Valley