For the Barnarians, rugby league star Sam Tomkins touched down in the corner in the final minute.
Adam Ashley-Cooper was named man of the match, despite receiving a yellow card.
After victories by the Barbarians over New Zealand and South Africa in 2009 and 2010 respectively, a close match had been expected. It was not to be. That Australia butchered three tries in the first half exemplified the one-sided nature of the contest.
Yesterday's win in front of 51,112 fans improved Australia's win-loss record against the Barbarians to 9-3 and eclipsed the previous record scoreline of 55-7 in Sydney in 2009.
Australia will face a much sterner test against Wales in Cardiff on Saturday in a rematch of last month's third-place playoff at the World Cup.
There is a concern over the fitness of second five-eighths Berrick Barnes after he received an accidental knee to the back and had to be replaced before halftime.
"He has had an x-ray and been cleared. There is no fracture but he is sore," coach Robbie Deans said.
Uncapped Queensland Reds centre Ben Tapuai, who played the majority of the Twickenham match, is set to make his test debut if Barnes fails to recover.
O'Connor had scans on his right hand, trampled in the first half, but was confident of playing next weekend.
"He did well," Deans said of O'Connor. "The test match will be a different kettle of fish but, like the team, he will be much better for that time."
O'Connor opened the scoring with a penalty, a reassuring start after his troubles with the boot against England at the same ground last year.
Barbarian Tomkins knocked on with his first touch in rugby union as Australia dominated the first half, despite having Ashley-Cooper and James Slipper sin-binned at different stages.
In his first appearance for the Barbarians, former Wallabies skipper Stirling Mortlock produced a bone-crunching hit on Australia captain David Pocock in the 20th minute.
However, there was little for the home fans to cheer outside of Tomkins' late try and a bizarre moment on the stroke of halftime.
With O'Connor having been judged to have commenced his attempt at conversion on the sideline, Barbarians halfback Peter Stringer raced out to charge down the ball.
With O'Connor not budging, the Irishman checked with referee Romain Poite before running off with the ball for halftime.
- AAP
