McCarron, the Charles Schwab Cup points leader and a three-time winner this year, birdied the par-5 16th and par-3 17th in a bogey-free round at Warwick Hills, the longtime home of the PGA Tour’s defunct Buick Open.
Goosen, the Senior Players Championship winner for his first victory on the 50-and-over tour, bogeyed the 17th.
Gillis finished his bogey-free round with a birdie on the par-4 ninth.
Bernhard Langer topped the group at 68.
Fred Couples opened with a 70. He won the 1994 Buick Open.
Defending champion Paul Broadhurst shot 71.
Two-time major winner Angel Cabrera had a 72 in his tour debut.