David Wachman’s 1000 Guineas heroine Legatissimo looked set to become a dual Classic winner when coming out of the pack to lead passing the furlong marker, but Colm O’Donoghue conjured a late rattle from 50-1 shot Qualify and got up by a short head.
Lady Of Dubai was a further two and a half lengths back in third.
Qualify mixed it with the best as a juvenile last season and won a Group Three along the way, but looked to have plenty on her plate having finished stone last in the Guineas at Newmarket and down the field in the Irish equivalent.
O’Donoghue dropped his mount out towards the back of the field for much of the mile-and-a-half journey and she remained nearer last than first rounding the home turn.
Legatissimo was the 5-2 favourite to become the first filly since Kazzia in 2002 to follow up Guineas glory in the Oaks and having travelled well for Ryan Moore, she quickened to the lead, but Qualify – who avoided trouble on the inside – wore her down in the dying strides.
Lady Of Dubai ran a perfectly respectable race in third. The biggest disappointment was Crystal Zvezda, who refused to settle for Richard Hughes and finished well down the field.
O’Donoghue, from Buttevant in Co Cork, said: ‘‘I’m not surprised, she’s always shown a lot of pace and is a well-balanced filly.
“Because she shows so much pace we were unsure if she’d get the trip, but she saw it out really strong.
“She travelled and she’s well balanced, so even though I was a long way back coming up the straight with a clear run, it’s the winning post that matters. I just wanted to keep her on an even keel and not interfere, she came home strong.
“They are new owners (Mrs Chantal Regalado-Gonzalez) so I’m delighted for them and I’d like to thank Mr Magnier, Mr Tabor and Mr Smith for the opportunities they continue to give me.”
O’Brien said: “She was always very classy and won her Group Three at the Curragh very easy last year. We thought we’d start at Newmarket, go to the Curragh and then come here. It went a little bit wrong at Newmarket, but Joseph (O’Brien) looked after her. She ran a real lovely race at the Curragh and we knew stepping up in trip would suit but weren’t sure about a mile and a half.
“She’s by Galileo, they are usually tough, and Colm gave her a masterful ride. We’re lucky, we have high-class horses and she’d always worked like one. I was just a bit worried the ground wasn’t fast enough.