Green Moon has already won the country's biggest horse race and prominent owner Lloyd Williams has declared the import to be in top shape ahead of his bid to add Sydney's richest race to his haul.

The seven-year-old has not won since his 2012 Melbourne Cup success but Williams is convinced the last-start Australian Cup runner-up is ready to run a big race in Saturday's $4 million Queen Elizabeth Stakes at Randwick.

"He's as good as we had him in 2012 going into the Turnbull and subsequently going into the Melbourne Cup," Williams told Melbourne radio station RSN.

"He's in great order. I think he'll run well."

Williams says Green Moon races best when he can position near the speed and the owner has confidence in Hugh Bowman to ride the galloper to his strengths.

"He's my favourite jockey in the world, Hughie Bowman, so he'll know what to do with him even though he has never ridden him," Williams said.

Bowman has already enjoyed plenty of success during the autumn with a Group One win on each of the past three Saturdays, highlighted by Criterion's Australian Derby triumph.

His success for Macedon Lodge has included last year's Sydney Cup on Mourayan and a Metropolitan Handicap victory on Seville.

Bowman won last year's Queen Elizabeth Stakes on the Chris Waller-trained import Reliable Man.

Green Moon has never been tested on heavy going and Williams admits he doesn't know how the horse will handle a rain-affected track.