This is the first event of the 2002 Buy.Com season, with half of the field consisting of Buy.Com players and the other half representing the PGA Australasia Tour. It also marks the first time a U.S. Tour has co-sanctioned an event with the PGA Australasian Tour.
Bryce Molder posted the best score for the Buy.Com players with a 3-under 69. He finished alongside New Zealand's Richard Lee one stroke behind the leaders.
O'Malley, who upset Tiger Woods in the first round of the WGC-Accenture Match Play Championship, had six birdies and two bogeys on his round.
'I felt really good out there today,' said O'Malley. 'I just kept it in play all day and only used the driver four times.'
Johnson, who earned his first victory on the European Tour at the ANZ Championship in Sydney earlier this year, birdied seven holes to counter three bogeys. The Swede credited his short game for his share of first place.
'My wedge came good today, it was something else,' said Johnson. 'I laid it up five times inside two feet. It's pretty easy to play golf when you don't have to putt much.'
All three leaders got their rounds off early, before windy conditions made it difficult for the afternoon groups at Kooyonga Golf Club.
A group of four were knotted at 2-under 70, including Germany's Alex Cejka. He was joined by the Australian trio of Stephen Leaney, Peter Fowler and Brad Kennedy.
Virginia Beach Open winner Trevor Dodds headed a larger group tied at minus-one.
Two-time Australian Open winner Aaron Baddeley, who was looking to perform strongly in the joint-sanctioned event with hopes of earning a breakthrough victory on the American circuit, struggled to a 12-over 84.
'Obviously I didn't play very well, I didn't drive well and obviously the bad shots got extremely penalized,' he said.
Full field scores from the Jacob's Creek Open Championship