K.J. Choi posted a bogey-free, 6-under-par 66 to earn the first-round lead at the Ally Challenge on Friday in Grand Blanc, Mich.

The South Korea native made four of his six birdies on the back nine at Warwick Hills Golf & Country Club, enough to take a one-shot lead over a four-way tie for second.

Brett Quigley, David Branshaw, Stewart Cink and Australia’s Rod Pampling are knotted at 5-under 67. Another group tied at 4-under 68 includes Glen Day, Bob Estes, Joe Durant, Jason Caron and Australian Greg Chalmers.

Choi, 54, is a month removed from the biggest accomplishment of his senior career — a victory at the Senior Open Championship, his first major title of any kind.

“This year I’m all better when I strike the ball,” Choi said. “Usually my driving, too much cut it and then little good fade, but this time is a very strike the ball. … Very happy today.”

Quigley, 55, started his round on the back nine and birdied five of his first seven holes. He got to 6 under with another birdie at the par-5 first, but he bogeyed the next hole and stayed at 5 under the rest of the day.

It was a pleasant surprise for a player who withdrew from the past two PGA Tour Champions events while nursing multiple injuries.

“I’ve had some good success here before, so I feel comfortable here,” Quigley said. “I really got off to a nice start, just kept making some putts, hit it close and had some good chances. Yeah, I just feel comfortable here and happy. Honestly, my goal this week was just to finish three rounds, so I have to do that two more days, so we’ll see how it goes.”

Of the quartet tied at 5 under, only Pampling kept his card bogey-free.

“Everything’s been close but just hasn’t had anything click all year,” Pampling said. “Even the start of the week wasn’t feeling good and I just had a feeling that I went with on Thursday in the pro-am, and it started coming around.”

Charles Schwab Cup money leader Ernie Els of South Africa opened with a 2-under 70.