England fast bowler Mark Wood has dismissed opener David Warner, having the dangerous left-hander caught behind.
Warner attempted a half-hearted drive on the last ball of the sixth over and Wood drew an edge, fill-in wicketkeeper Ollie Pope taking the catch.
Australia are 1-12 and lead by 134.
"This is a good delivery over the wicket, nice line, nice length," said former England captain Michael Vaughan on Fox Cricket.
"David Warner ... just hanging back again.
"Brilliant again from Mark Wood."
Openers David Warner and Marcus Harris have seen out the first three overs of Australia's second innings.
The hosts are 0-8 and leading by 130, with Warner yet to get off the mark and Harris on eight.
England reviewed an LBW call on Harris on the fifth delivery of the third over, off the bowling of James Anderson, but ball tracking showed the ball would have been going over the stumps.
By Zachary Gates07 Jan 2022 23:43
England have been bowled out for 294 early on day four – and Scott Boland was again the architect of the tourists' demise.
Off-spinner Nathan Lyon removed Jack Leach and Boland then captured the final two wickets, dismissing centurion Jonny Bairstow and tail-ender Stuart Broad.
Boland has finished with figures of 4-36 from 14.1 overs, taking his Test career record to 11-91 at 8.27.
"What a start to his Test career," said former England quick Isa Guha on Fox Cricket.
Leg-spin legend Shane Warne labelled the start to Boland's Test career "unbelievable".
Australia's David Warner and Marcus Harris will be back in the middle soon, looking to build on the hosts' lead of 122.
By Zachary Gates07 Jan 2022 23:35
Australia have received a major boost early on day four, with white-hot quick Scott Boland returning to bowling after yesterday's nasty tumble.
Boland underwent scans after taking a fall on his follow-through on the final ball of the second session.
The bustling Victorian, who remarkably took 6-7 to spearhead Australia's MCG victory, hasn't taken long to have an impact on day four at the SCG, removing England centurion Jonny Bairstow.
England are 9-289, in reply to Australia's 8-416 declared, and Stuart Broad and James Anderson are in the middle.
By Zachary Gates07 Jan 2022 23:33
Welcome to Wide World of Sports' live coverage of day four of the fourth Ashes Test.