Bill Lunde, who held a share of the overnight lead, bogeyed four of the last six holes to close with a 1-over 73. He ended in a tie for second place at 3-under-par 285. He was joined there by Bradley Hughes (71) and Brendan Jones (71).
Peter Senior, who shared the overnight lead with Lunde, struggled to a 2-over 74. He shared fifth place with former PGA Tour winner Franklin Langham and Euan Walters, who won the Jacob's Creek Open Championship last week, at 2-under-par 286.
Coles was under the radar most of the round. He birdied the fourth, but stumbled to a bogey on No. 6. Coles fought right back to birdie the very next hole. He parred the next two holes to head to the final nine at minus-3.
Doug Barron, who finished at even-par 288, birdied the second, that created a five-way tie for the lead at minus-4. Later, while Coles was not making much noise on the front side, Lunde surged to 7-under par with a birdie at the 10th.
As those players stumbled, Coles made his move on the back nine. He birdied the 10th and 12th to get to 5 under, two behind Lunde. Coles bogeyed the 13th, but came right back to birdie the 14th. Lunde meanwhile bogeyed back-to-back holes to drop into a share of the lead with Coles.
Coles parred three straight holes before dropping in a birdie on No. 18 at the Clearwater Resort to secure the win. The title is his second on tour as he previously won the 2002 Jacob's Creek Open Championship.
Lunde, who had five birdies, a bogey and a double-bogey on the front side, bogeyed each of the last two holes to finish three back.
Jones carded three bogeys and two birdies on the front side, before picking up three more birdies on the back nine. He also bogeyed the 13th en route to a share of second place for the second straight week.
Hughes picked up four birdies on the front side, but stumbled to three bogeys down the stretch to fall into a share of second.
Barry Cheesman and Scott Sterling shared eighth place at 1-under-par 287. Barron was joined at even-par by Richard Best.
Jess Daley and Jon Mills led a group of eight players at 1-over-par 289. They were joined there by Shane Bertsch, Tony Carolan, Lucas Parsons, Paul Sheehan, D.A. Points and Vance Veazey.