Mark James, the 1999 European Ryder Cup captain, Rafael Navarro, Bobby Walzel and 17-time European Tour winner Mark McNulty each posted rounds of 5-under-par 67 to share second place.
Gale, 57, and a five-time winner on the European Seniors Tour, including three this year, was 1 under as he made the turn at the TPC at Eagle Trace. He collected five birdies on the back nine to surge into first place.
Bob Bailey and Mark Johnson are tied for sixth place at 4-under-par 68.
Mike Smith, who played on the Champions Tour last season, shot a 3-under 69 and is tied for eighth place with Ed Sabo and Jack Spradlin, who finished third in the 2001 Q-School.
Sam Torrance, the 2002 European Ryder Cup captain, carded a 1-under 71 and is part of a group tied for 15th place along with Joe Inman, a three-time winner on the elder circuit.
Seiji Ebihara, the runner-up at Q-School in 2002, struggled to a 4-over 76 on Tuesday and is part of a group in 88th place.