The duo finished regulation tied at 17-under-par 271 and after one playoff hole, with darkness approaching and both players exhausted, they agreed to share first place.
Moseley was one of many players who returned to Hyatt Coolum Resort early Sunday to complete the third round after thunderstorms suspended play on Saturday. Moseley picked up two birdies on the inward half and owned a five-shot lead after 54 holes.
However, Moseley could not carry his momentum over to the final round as rain delayed play again.
When play resumed, Lonard tied Moseley atop the leaderboard with a birdie at the 12th to reach 17-under but ran into trouble with a bogey at the very next hole.
At the 15th, Lonard again grabbed a share of the lead with a birdie only to give that stroke back with a bogey at the 16th.
Lonard stepped onto the final tee with a one-shot deficit. Moseley saved par after he sent his tee shot in the sand at 18, leaving Lonard to drain a 50-foot putt for birdie to force a playoff.
The end result marked the first time in Australian tournament history that a title was shared.
Stuart Appleby, who won the Australian Open in 2001, carded a final-round 67 to finish three shots back at 14-under-par 274. Greg Norman was one shot further back at 13-under-par 275.
Greg Chalmers finished alone in fifth at 12-under-par. Aaron Baddeley struggled with a closing 73 to finish six shots off the pace at 11-under-par 277.
Adam Scott finished alone in seventh place at 10-under-par 278.
Full-field scores from the Australian PGA Championship