The trio all clinched qualification on Wednesday. Australia were the first to book their ticket with a 1-1 draw in North Korea to finish top of Group A, three points ahead of Iraq.
South Korea drew 0-0 at home to Bahrain to clinch top spot in Group B and a sixth consecutive Olympic appearance.
The Koreans were unbeaten in the group but drew their last three matches 0-0.
Japan won Group C by a two-point margin and clinched their place in the Chinese capital with a 0-0 draw at home to Saudi Arabia.
