Overnight leader James Nitties, who was playing in only his fourth event as a professional, carded a 2-under 70 to take second place at 16-under-par 272. Bob Estes was one shot further back at 15-under-par 273.
Lonard began the day three shots behind Nitties and hung around with pars over his first three holes. Lonard then birdied two in a row starting at the par-5 fourth but found trouble with a bogey at the sixth.
The Australian recovered at the par-4 seventh with the first of four consecutive birdies. That run lifted Lonard to the top of the leaderboard and he added a birdie at the par-4 16th to pad his advantage.
The 37-year-old, who titled at the NSW Open the week before he won the Australian Open, parred his two remaining holes for his third straight victory.
Nitties stumbled early with a bogey at the third but recovered well with birdies at the fourth and the fifth. The 22-year-old remained in control with a birdie at the eighth but cooled down around the turn, eventually losing ground to Lonard.
Nitties bogeyed the 14th to fall further off the pace but came back with a birdie at the 16th.
Former U.S. Open champion Corey Pavin joined Nick O'Hern in a tie for fourth at 14-under-par 274. Peter Senior, who won this event last year, followed at 13-under-par 275 along with John Senden and Adam Crawford.