Mother Earth and Empress Josephine head the field for the race at 4.20pm as former Classic winners.
And Irish trainer O’Brien said: “Both fillies are in very good form and we are looking forward to the race with them. Mother Earth has been in good form since France. She seems to have come out of the race well.
“Empress Josephine is progressing nicely and has come out of the Curragh well. She hasn’t done a lot since but she seems to have taken the race well.”
Mother Earth won the 1,000 Guineas at Newmarket in May but came up short in completing the double in the French 1,000 Guineas at Longchamp.
The ground in France was far too soft for her liking with the slightly firmer turf at Ascot, while was also declared soft before racing on Friday, expected to translate to her return to front-running form alongside Irish 1,000 Guineas winner and stablemate Empress Josephine.