The 62-year-old Mast, winless on the 50-and-over tour, had five birdies and two bogeys. he birdied the first three holes before the wind picked up.
"That's always a good start," Mast said. "I three-putted the fourth and then the wind started getting heavier. I think we got a little bit of a break playing second off. It was windy, but not as windy as it is right now. I got a chance to play four or five holes without a real heavy wind and that's already an advantage. You never know when you are going to get a break, but I think I did."
It is the first time Mast has had an outright lead in 165 Champions Tour starts.
"I played pretty solid," Mast said. "I'm usually a pretty good wind player. It's hard. You've got to control your ball in the wind. You've got to have a good short game. I made some key putts here and there to keep the momentum going."
Kenny Perry, the Senior Players Championship and U.S. Senior Open winner in consecutive tour starts this summer, opened with a 70 on the tree-lined layout.
"Interesting day," Perry said. "I got off to a good start but I wasn't making any birdies. I was hitting the ball nicely and that wind was very difficult."
He's making his first appearance in the event.
"People have been wonderful here," Perry said.
Bernhard Langer was another stroke back along with Mark Brooks, Mike Reid, Tom Pernice Jr. and David Frost.
Mark Calcavecchia, the winner last year on the adjacent Vercheres layout, had a 74. He missed the tour's previous two events because of back problems.
Rocco Mediate, coming off a blowout victory Sunday in Calgary, Alberta, opened with a 75. Last week, he shot 63-64-64 for a seven-stroke victory.