Fellow Australians Peter Senior, Geoff Ogilvy, Robert Allenby and Jarrod Moseley were all tied for third at 5-under 67 on the par-72, 6,996-yard Huntingdale course.
Ryan Palmer was the top American after a 1-under 71. Rich Beem, the 2002 PGA champion, opened with a 2-over 74.
Lonard made five birdies in the first nine holes, reaching the turn at 5 under. He eventually went to 8 under. But Lonard bogeyed the par-3 15th and also the 18th, where he three-putted from 65 feet.
Lonard, the defending champion and 1997 winner, said the key was taking chances early and hoping to squeeze by on the closing holes.
'You've got to go as hard as you can as early as you can around here,' Lonard said. 'You have to take your chances on the front nine, because the finishing holes have a habit of jumping out and grabbing you.'
Senior, who won at Huntingdale in 1995, said despite his opening 67, his putting and short game is hurting.
'I've had the yips for a long, long time,' Senior said. 'It has slowly crept through to my short irons, especially from 50 or 60 yards away.'
Rain and thunderstorms forced a 30-minute postponement in play early Thursday.
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