Brooks, winner of the 1996 PGA Championship, shot a 6-under 65 at the Glen Oaks Country Club course to lead by two over Mark Calcavecchia and Peter Senior.
Brooks posted his best score since joining the Champions Tour. His round was highlighted by a 65-foot putt at the par-4 17th for his third consecutive birdie.
He has not had the first-round lead of a tournament since the 2006 B.C. Open on the regular PGA Tour.
John Huston, who turned 50 Wednesday and thus became eligible for the senior circuit, shot a 70 in his debut. Also making his debut was Damon Green, who has been the caddy for former Masters champion Zach Johnson since 2003. He shot a 75.