Apart from Gill, who was capped with the Sevens side, the squad included uncapped back-rower Schatz of Waratahs and lock Kane Douglas.
Robbie Deans says his squad for the inaugural Rugby Championship includes an injection of players in positions in which Australia has historically lacked depth and has hailed the form of veteran lock Nathan Sharpe.
Gill and fellow openside flanker Michael Hooper, who earned three caps in the June Tests, will give Deans the luxury of providing quality backup to Wallabies captain and starting No.7 David Pocock.
Halfback Will Genia’s understudy Nic White is also awaiting his first cap after being restricted to the bench during his first involvement in a Wallabies squad in June.
“There’s an injection of players in areas where we historically haven’t had a lot of depth, openside being an obvious one which is great for those two blokes (Gill and Hooper),” Deans said on Tuesday.
“Michael Hooper has had a taste and introduction and Liam fulfilled his obligations to the (Australian) under-20s before we involved him in this instance.
“It’s good to have those two points of enthusiasm added to the group.
“Schatzy obviously gets rewarded for his efforts through Super Rugby, where he’s been very consistent and he’s grown rapidly.”
Deans said Douglas earned a spot ahead of Rebels rookie and former rower Cadeyrn Neville on the basis of his greater set-piece experience.
Douglas joins a second-row contingent including 105-Test veteran Sharpe, who postponed his retirement to help the Wallabies, following the long-term injury to fellow lock and first-choice captain James Horwill.
“Sharpey is probably playing the best rugby of his career, to be honest,” Deans said.
“It becomes very clear when the end looms and he’s enjoying his rugby.
“Deans said Sharpe might even want to revisit his decision to retire, though the 34-year-old second-rower last week stressed he had no intention of playing on next year.
The coach said injured backs James O’Connor and Pat McCabe would not be considered before Australia’s third Rugby Championship game against South Africa in Perth on September 8.
Wallabies squad:
Ben Alexander, Adam Ashley-Cooper, Berrick Barnes, Kurtley Beale, Quade Cooper, Dave Dennis, Kane Douglas, Anthony Faingaa, Saia Faingaa, Will Genia, Liam Gill, Mike Harris, Scott Higginbotham, Michael Hooper, Rob Horne, Digby Ioane, Sekope Kepu, Drew Mitchell, Stephen Moore, Nick Phipps, David Pocock (captain), Tatafu Polota-Nau, Benn Robinson, Radike Samo, Jake Schatz, Nathan Sharpe, Rob Simmons, James Slipper, Sitaleki Timani, Nic White.