Petersen, who entered the week 155th on the money list, fired rounds of 65-69-65-69 on the Empire Lakes golf course for a 20-under-par total and a four-stroke victory over six others.
Petersen began the day tied for the lead with Fran Quinn. But Quinn struggled to a 3-over-par 75 on Sunday to tie for 11th. The tournament was ultimately decided on holes 7-10. Still tied through the first six holes, Quinn played that four-hole stretch in 3-over-par. Petersen played holes 7-10 in 3-under.
Petersen, who missed 10 cuts in his first 11 starts this year, earned $72,000 for his first-career victory. He jumped to 60th on the money list; however, this was the final full-field event of the season.
The top 55 in season earnings will play in the Tour Championship at the Highland Oaks Golf Club in Dothan, Ala., in two weeks.