Digby Ioane, Lachie Turner and James Horwill all scored twice, while Rob Horne and Radike Samo also touched down for the Wallabies and James O'Connor kicked 20 points on his first start at fly-half.
The Barbarians' defence was embarrasing and they conceded 42 second-half points, but they did give the 51,212 crowd a late cheer with a consolation try for England rugby league international Sam Tomkins.
Danny Cipriani, on his first appearance at Twickenham since the 2008 autumn internationals, kicked two first-half penalties for the Barbarians.
South African lock Victor Matfield captained the invitational team in the last game after a stellar 110-cap career.
At the other end of the scale, Tomkins was playing his first rugby union game, a week after facing Australia in the Four Nations final.
Tomkins acquitted himself well - far better than Willie Mason did in similar circumstances against England in May - and did not look out of place at Twickenham.
The Wigan full-back started on the wing and could have scored in the first half had Bryan Habana not ruined a scintillating break with a careless forward pass.
O'Connor twice kicked the Wallabies into the lead, first with a penalty and then a drop-goal, and he will compete with Cipriani start at fly-half for the Melbourne Rebels next season.
O'Connor carried the ball to the line, testing the Barbarians defence, but his inexperience in the role was exposed when Robbie Fruean picked off a telegraphed pass inside his own 22.
Fruean, who starred at Twickenham in the Crusaders' Super 15 victory over the Sharks earlier this year, streaked clear but failed to find Tomkins on his shoulder.
Fruean delayed his pass to Tomkins for a split-second too long, allowing Adam Ashley-Cooper to get his hand to it. The Wallabies full-back was sin-binned for the deliberate knock-on but the try was saved.
Cipriani landed the penalty, O'Connor slotted his drop-goal and then, a minute after Ashley-Cooper's return to action, Australia scored their first try.
Stirling Mortlock was guilty of running out of the defensive line, which left a gaping hole in the Barbarians defence for Ioane to beat Cipriani to score.
The Wallabies were reduced to 14 men for a second time when prop James Slipper shoulder-charged Cipriani late, but the Barbarians could not take advantage.
O'Connor and Scott Higginbotham butchered golden opportunities with forward passes but the Wallabies secured an 18-3 half-time lead with a try in the corner from Turner.
Ashley-Cooper launched the counter-attack from a stray kick and, after quick hands from O'Connor and David Pocock's drive, the ball was moved wide for Turner.
In unusual circumstances, O'Connor was denied the chance to convert from the touchline after Peter Stringer raced out to pick up the ball.
Turner's score was a sign of things to come and it was one-way traffic after the interval as Australia found their accuracy with four tries in 13 minutes.
Replacement James Horwill charged over after Stephen Moore, on the wraparound from a lineout, made the dent before offloading to the Wallabies' World Cup captain.
The Barbarians lost Salvatore Perugini to the sin-bin and Australia piled forward.
Cipriani gathered an overthrown lineout in his own 22 but was guilty of an ill-judged offload, which Horne picked off to score.
Horwill added his second with a powerful run onto Nick Phipps' short pass, fending off two defenders to touch down before Turner took advantage of another scything break from Ashley-Cooper to score Australia's sixth try.
Ioane drove through two Barbarians defenders to bring up the half-century of points and Samo's burst from the back of the scrum completed the rout.
The Barbarians finally scored with the last play of the match when Cipriani showed great hands to pick up a pass off the deck and Tomkins scored one-handed in the corner.
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.