Leishman earned $94,500 to jump from 56th to 19th on the money list with $197,926. The top 25 after the final three events will earn 2009 PGA Tour cards.
Leishman, the 2006 Jisan Resort Open winner on the Korean PGA Tour, had a 21-under 267 total on the Midland Country Club course. He opened with rounds of 67, 66 and 66. The 11-stroke matched the tour record set by Chris Smith in the 1997 Omaha Classic.
"I was determined to get off to a good start," said Leishman, who did just that with a birdie at the par-5 second hole and an eagle at the fourth. "When I made the eagle at 4, I was able to play more conservative."
Leishman used a 2-iron off the tee after establishing the large lead.
"It was a really handy club to have in the bag this week," Leishman said.
Dallas resident Keoke Cotner shot a 68 to finish second at 10 under.
"I've played at Midland every year, so I'm pretty familiar with it," Cotner said. "The wind was howling, but the difference for me this week was I didn't make as many bogeys."