Idaho is set to try two miles for the first time in the Qatar Goodwood Cup on July 31.
The full-brother to Highland Reel won over an extended mile and five furlongs in the Ormonde Stakes at Chester in May.
He was odds-on favourite for the St Leger two years ago, but unseated Seamie Heffernan after stumbling in the straight.
Trainer Aidan O'Brien said: "The plan is to go to the Goodwood Cup with Idaho. We want to try him over the two miles and see. We always felt he would stay further than a mile and a half.
"We went beyond a mile and a half once and that was at Chester and he got that very well."
Order Of St George will not be seen at Goodwood, with immediate plans likely to be decided by the weather.
O'Brien's former Gold Cup hero has shown himself to be equally adept at a mile and a half, finishing fourth in last year's Prix de l'Arc de Triomphe and third the year before.
He was last seen when fourth to Stradivarius when attempting to regain his Gold Cup crown at the Royal meeting.
O'Brien said: "You won't see him at Goodwood. He could appear in the King George if the rain came, but if it didn't he will be left alone and have a prep for the Irish St Leger.
"He is in good form at home."
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