Stadler, who won the Xerox Classic earlier this year, finished at 20-under-par 264. That total gave him the new tournament scoring record. Mike Sposa set the old record of 265 in 1998.
'This means everything, it's great,' said Stadler, who collected $108,000 for the win and guaranteed himself his PGA Tour card for 2007. 'To be freed up for the rest of the year and not have to worry about Q-school and that whole mess, it's fantastic.'
Glen Day briefly held the lead during the final round, but came up one short despite a final round 6-under 65. Day ended at 19-under-par 265.
Jason Allred carded his fourth round in the 60s on Sunday and ended alone in third. Allred posted a 5-under 66 to finish at minus-17. Scott Dunlap took fourth at 16-under-par 268 after a 67, while third-round leader Mario Tiziani was one stroke further back after a 2-over 73.
With Tiziani not being able to hold on for the win, that makes it 12 straight events on the Nationwide Tour that the 54-hole leader has not gone on to win.
Stadler began the day two strokes behind Tiziani. The lead was down to one after three holes as Tiziani bogeyed two, then matched Stadler's on three.
The 26-year-old Stadler then dropped in a 5-foot birdie try on four to gain a share of the lead. There was a big swing on six where Tiziani stumbled to a bogey, while Stadler drained a 12-foot birdie putt to move two clear.
Stadler parred four straight, then faltered to a three-putt bogey on 11. He parred three in a row from there and was joined in the lead by Tiziani and Day.
Tiziani drained a 14-footer for birdie on 12 to join Stadler at minus-17. Meanwhile, Day was 2 under through nine holes then dropped in back-to-back birdies from the 11th to join Stadler and Tiziani in the lead.
The 36-year-old Tiziani dropped a shot on the 14th and wasn't a factor again. He also bogeyed the last to end five back.
Day, playing a group ahead of Stadler, birdied the 15th to move one up.
Stadler responded by sinking a 5-footer for birdie on 15. He came right back with a two-putt birdie on 16 at Hillcrest Country Club. Stadler drained a 12-footer on 17 after Day made a 5-foot birdie putt on the same hole.
At the last, Day knocked his second shot to the back fringe and he two-putted for par from there. Stadler found the fairway off the tee, then pulled his approach shot left of the pin into the fringe. He putted to 3 feet and calmly tapped that in for par and the win.
'I didn't hit it all that great on the back nine until I hit that pretty lucky bunker shot on 15 for the birdie,' Stadler stated. 'Then I hit a couple good ones coming in. But I had to give myself that mini-heart attack on the last.'
For Day, it was his second runner-up finish of the season and both times he finished second to Stadler.
'I gave Kevin this on a silver platter. I know that and everyone else knows it,' Day admitted. 'Today I did the best I could do. I played solid. I didn't make a bogey. Yeah, I'd like to have the putt back on the par-5 (16), but I don't feel like I hit a bad putt.'
Tripp Isenhour and Andrew Buckle shared sixth at 13-under-par 271. Jess Daley and Jason Dufner closed with rounds of six-under 65. They were joined in eighth place at minus-12 by Brendon De Jonge, Franklin Langham, Jarrod Lyle and Jay Williamson.