Newmarket Handicap winner The Quarterback will be racing for a trip to Royal Ascot when he runs at Moonee Valley.

The William Reid Stakes on Thursday night, Melbourne's final Group One race of the season, will give trainer Robbie Griffiths his guide whether Royal Ascot is a reality, or a dream.

With The Goodwood in Adelaide in May firmly in his mind, Griffiths has scrapped any thoughts of running the horse in next month's TJ Smith at Randwick.

"I'd love to go to Ascot and the horses that have succeeded there have been proven at weight-for-age," Griffiths said.

"If he bombs out in Sydney going in as an underdog, going the other direction, at weight-for-age, against locals on their home track, I won't know if it's because those reasons have stopped him or he's genuinely not good enough."

Griffiths says Moonee Valley is not an ideal track for The Quarterback who finished seventh behind Chautauqua in the McEwen Stakes over 1000m there last spring.

"If he can hold his form and go to the Goodwood, run well, then we know for sure that we're on the right wavelength going to Ascot," Griffiths said.

"If we don't measure up, we just don't go."

Griffiths has started plans for Royal Ascot with the King Stand Stakes on the opening day of the five-day meeting the preferred option.

He said bookings had been made and The Quarterback had been inoculated.

"It's all up to the horse now," he said.

"What will make the decision is the horse's form, whether the owners want to spend the money and if he shows he's up to weight-for-age.

"He ticks the straight box, so that's why it's appealing."

Griffiths, who landed his first Group One victory when The Quarterback won the Newmarket Handicap on March 12, will also saddle It Is Written in Thursday night's race.

But Griffiths said he faced a tough task from barrier nine of 12.

"I reckon he would have been a little chance if he had drawn one to four and got an easy run," Griffiths said.

The Quarterback is a $13 chance with It Is Written at $41 while last year's winner Lucky Hussler heads the market at $3.40.