Waratahs playmaker Barnes impressed in all three summer wins over Wales but Cooper's return to fitness following a lengthy lay off had meant there was plenty of debate regarding the fly-half berth ahead of today's team announcement.
Cooper's limited game time since his recovery from the ACL injury he suffered in October's third-place play-off at the World Cup left Barnes as the favourite to face the All Blacks, though, and head coach Robbie Deans has decided not to take a risk on the maverick Reds star for the first of three Bledisloe Cup encounters.
"Berrick played very well through June and we had good continuity prior to the mishap with Pat McCabe, so it was pretty straightforward," said Deans, who refused to rule out the possibility of Cooper returning to the side sometime during the tournament.
"There's not a lot of certainty in this industry…(Cooper needs to) keep doing what he's doing - keep working with us.
"I've got no doubt he'll get an opportunity again, absolutely."
Elsewhere in the Wallaby line up, Anthony Fainga'a has been given the nod at inside centre following injury to Pat McCabe, with Deans deciding to name just two backs replacements in the shape of scrum-half Nick Phipps and wing Drew Mitchell.
Newly-crowned Waratahs Player of the Year Dave Dennis starts at blindside flanker in the second of just two changes to the XV that began the third-Test win over the Welsh, with Scott Higginbotham moving to No8 in place of injury-victim Wycliff Palu.
David Pocock skippers the side in the continued absence of regular captain James Horwill, while Nathan Sharpe starts alongside Sitaleki Timani in the second row despite having retired from club rugby earlier this year.
Australia (vs New Zealand, Sydney, August 18)
Kurtley Beale, Adam Ashley-Cooper, Rob Horne, Anthony Faingaa, Digby Ioane, Berrick Barnes, Will Genia; Benn Robinson,Tatafu Polota Nau, Sekope Kepu, Sitaleki Timani, Nathan Sharpe, Dave Dennis, David Pocock (capt), Sott Higginbotham
Replacements: Stephen Moore, James Slipper, Rob Simmons, Radike Samo, Michael Hooper, Nick Phipps, Drew Mitchell