Host nation Australia and two-time champions South Korea booked their places in the quarterfinals of the 2015 AFC Asian Cup after victories in Group A on Tuesday night.
With both sides earning six points from their first two matches, top spot in the group will come down to Saturday's match between them in Brisbane.
The Omanis were unbeaten in their three previous matches against the Socceroos and appeared unfazed by the occasion as they made life uncomfortable for the hosts. But two goals in three minutes saw Australia assert their dominance.
After the header from Trent Sainsbury in the box following a corner, McKay powered home from close range in the 27th minute. And then on the half hour, a lovely flick-on by Massimo Luongo set Kruse on his way. The Bayer Leverkusen forward's shot crept under Ali Al Habsi and Australia led 2-0.
Mark Milligan thought he'd extended the lead on the stroke of half-time when he found the back of the net. But instead of playing advantage, Japanese referee Ryuji Sato awarded Australia a penalty for an earlier infringement on Tim Cahill.
However, Milligan then slotted home the spot kick in first half injury time to give the Socceroos a 3-0 lead at the break.
Australia injected two new players in the second half: Tomi Juric replaced Cahill, while veteran midfielder Mark Bresciano came on for Massimo Luongo and took over the captaincy.
After Juric tested Al Habsi in the 68th minute with a strong shot, he put the Socceroos 4-0 ahead in the 70th minute. The tireless Matthew Leckie burst down the left and crossed to Juric whose first time effort hit the back of the net to give the Socceroos a comfortable win.
Earlier on Tuesday, South Korea defeated Kuwait 1-0 in Canberra for their second victory in the tournament after Nam Tae-hee's headed goal in the 36th minute.
South Korea made seven changes from the lineup that opened with a 1-0 victory over Oman to face Kuwait; injuries and illness forced a reshuffle for Uli Stielike's side.
Nam's first-half header was enough to give two-time champions a place in the knockout stages as they look to end a 55-year drought in the Asian Cup.
After a period of sustained pressure, Nam headed home a perfect Cha Du-ri cross nine minutes before half-time.
Kuwait had their chances to equalise in the second half as they produced a much improved performance compared to their opening match. But the loss means that the Kuwaitis and Oman are the first two nations eliminated from the 2015 tournament.
Information from Associated Press was used in this report.
