Jason Dufner matched playing partner Zach Johnson's birdie putt on the 17th hole Saturday and finished with a 4-under 66 for a one-stroke lead in the Colonial.
Dufner, who won the Byron Nelson Championship last week, saved par on the final hole after a wayward tee shot and finished three rounds at 15-under 195.
Johnson was second after a 65 and Tom Gillis a distant third at 7 under.
Dufner is trying to win for the third time in five weeks and attempting to join Ben Hogan as the only players to win both PGA Tour events in the Dallas-Fort Worth area in the same year. When Hogan did it in 1946, the events weren't played in consecutive weeks.