Sonoma, CA (My Sportsbook) - John Cook followed his course-record 62 on Friday with a five-under 67 on Saturday and is comfortably ahead after three rounds of the season-ending Charles Schwab Cup Championship.

Cook finished 54 holes at 19-under 197 and is six ahead at Sonoma Golf Club.

Cook got another record on Saturday, but this one wasn't just for Sonoma Golf Club. His 19-under 197 was the lowest 54-hole score in a 72-hole event in Champions Tour history.

"I just drove the ball nicely and hit it with some pace and hit a lot greens again," said Cook. "Just kind of did everything okay, so I'm quite pleased."

Russ Cochran shot a four-under 68 and is alone in second place at minus-13.

Brad Bryant posted a three-under 69 to finish three rounds at 12-under 204. He was joined at that number by Tom Watson, who carded a one-under 71 in Saturday's third round.

Cook wasted very little time in getting into red figures on Saturday. He almost holed his third shot from short of the green at the par-five second, but settled for a tap-in birdie.

Two holes later, Cook knocked his tee ball to six feet and converted the birdie putt. He parred his next three holes, then gave himself another tap-in birdie at the next par five at Sonoma, the eighth.

Cook parred three around the turn, but found trouble off the tee at No. 12. By the time he reached the green, Cook had 15 feet for par and the ball stayed above ground.

He atoned for the error at 12 at the par-five 13th. Cook reached the green in two and two-putted from just outside 20 feet for another birdie. He was 17- under par and five strokes clear of the field.

Cook saved par from a bunker at 14, then went on another birdie run.

At the 15th, Cook knocked his approach to nine feet and drained the birdie effort. He collected his fourth birdie at a par-five hole on Saturday with a three-footer at No. 16.

Cochran birdied 17 to get within six and it looked like Cook may trim his own cushion at the closing hole. He drove into a fairway bunker and couldn't advance his ball to the fairway. Cook hit his third to 10 feet and the 11-time PGA Tour winner calmly stroked home the par save to give him a six-shot lead with Sunday to go.

Cook will be in search of his fourth Champions Tour title on Sunday, but his second in just a short time. Two weeks ago, Cook won the Administaff Small Business Classic.

First-round co-leaders Jeff Sluman (70) and Phil Blackmar (72) were joined in a tie for fifth by Larry Mize (68) at minus-11.

Lonnie Nielsen managed a three-under 69 and is alone in eighth at 10-under 206.

This is the final event of the season and the year-long Charles Schwab Cup race will be determined on Sunday.

Loren Roberts led coming into the week, but after a one-over 73 on Friday, he appeared to be in jeopardy of getting his second $1 million payout in three years.

Roberts responded on Saturday with a six-under 66. He moved into a tie for 15th place at minus-seven and he is in good shape to claim the Cup. Fred Funk, Jay Haas and Bernhard Langer can mathematically catch him, but are each below him on the leaderboard.

"It was a good round when I needed to have one," said Roberts.

Defending champion Andy Bean shot a one-over 73 on Saturday and is tied for last at even-par 216.