Quigley, who started the day tied with Gary McCord, shot a 6-under-par 66 to climb to 13-under for the tournament; four shots clear of his nearest competitor, Jay Sigel.
Sigel raced into contention by firing his lowest round of the year, a 9-under-par 63. Hes in search of his first Senior PGA Tour title since 1998.
McCord is now tied for eighth at 6-under following a 1-over-par 73. Bruce Lietzke, the 13-time PGA Tour winner who turned 50 on Wednesday, followed an opening 74 with a bogey-free 66. Hes at 4-under-par, nine shots off the lead.
Quigley is a four-time winner on tour. This is his 139th consecutive start.
Full-field scores from the SBC Senior Open