The 51-year-old Simpson, a four-time winner on the PGA Tour whose career has been sidetracked by Lyme Disease and a series of injuries and other ailments, is winless in 44 starts in parts of three seasons on the 50-and-over tour.
"I shouldn't still be playing. I'm a walking miracle," said Simpson, who had brain stimulation surgery and an electrode planted in his head three years ago.
He had five birdies in a six-hole stretch in a back-nine 30. His previous best on the Champions Tour was a 65 last year in he SAS Championship.
"It's nice to play solid golf," Simpson said. "I missed a couple of short putts, but overall played well."
Johnson opened his bogey-free round with a 58-yard chip-in on his first hole.
"That was a nice little gift," Johnson said. "That got me going and I played pretty strong from there on."
Defending champion Jay Haas and Bernhard Langer opened with 65s, and Craig Stadler, Ben Crenshaw, Bruce Lietzke and D.A. Weibring shot 66s. Langer birdied all three of the par 5s, reaching the greens in two shots and two-putting.
"I played really solid, especially off the tee," Langer said. "It was probably one of my best driving days. I put myself in a lot of positions to attack the pins."
Scott Hoch, coming off consecutive wins in Florida in the Allianz Championship and The ACE Group Classic, had a 67. Mark O'Meara opened with a 69 in his first start of the year on the tour, and Scotland's Sandy Lyle shot a 70 in his Champions Tour debut. The two-time major champion turned 50 on Feb. 9.
