The Socceroos will now face an Iraq side with nothing to play for as they attempt to secure the victory to get them to next year's World Cup finals.
Iraq's 1-0 loss to Japan in Doha on Wednesday (AEST) means Australia's 4-0 smashing of Jordan in Melbourne on Tuesday night puts them in the box seat for World Cup qualification.
A win over the out-of-contention Iraqis in Sydney next week will book Australia's place at the expense of Jordan and Oman.
Jordan host Oman in Amman in the last of the Group B qualifiers next week, and the winners would need Australia to drop points to have any hope of securing the other automatic qualification bid.
The style of Australia's victory at Etihad Stadium - and the scoreline - were just what coach Holger Osieck was looking for ahead of next Tuesday's final qualifier.
Goals to Mark Bresciano, Tim Cahill, the outstanding Robbie Kruse and skipper Lucas Neill lifted Australia into second place in Asia's Group B.
"It was good to have a win like that which will definitely give a lot of confidence for the last game against Iraq," coach Holger Osieck said.
"We made a big step forward but we haven't crossed the finish line.
"That's a fact and I made it perfectly clear in the dressing-room to the players that the preparation for next Tuesday has started already."
Skipper Lucas Neill echoed his coach's sentiments amid quickly muffled euphoria following one of the team's most authoritative victories under Osieck.
"We told the guys that the job's not done," Neill said after scoring his first ever international goal in his 91st appearance for his country.
"It was a great team performance, fantastic result, clean sheet and just for once I'm going to be a little bit selfish, and be delighted I've capped it off with my first goal.
"There's been a fantastic focus and intensity ... and it's a straightforward equation.
"We know exactly what we've got to do with one match to go, and the prize is Brazil."
Kruse and Bresciano were outstanding, creating and sharing among the goals.
Kruse provided Bresciano a cross on a plate after neat lead-up work for the Socceroos' first in the 15th minute.
Then the Bayer Leverkusen winger set up Cahill for a second - a header just after the hour - before turning scorer himself with a memorable Australian third.
Kruse nutmegged a defender with a blind turn and slammed home in the 76th minute, before Neill delighted the 43,000-plus fans with a fourth six minutes from time.
In Doha, Shinji Okazaki scored in the 89th minute to ensure already-qualified Japan topped Group B and ended Iraq's slim hopes of making the World Cup finals, regardless of remaining results.
In Group A, South Korea beat Uzbekistan 1-0 to move within a point of progressing to Brazil.
South Korea lead with 14 points, three clear of Uzbekistan, which conceded a first-half own goal by Akmal Shorakhmedov in Seoul.
Iran beat Lebanon 4-0 to move into second place in that group.