Irish 1,000 Guineas winner Pleascach chased down 15-8 favourite Covert Love to win the Yorkshire Oaks at York's Ebor Festival.
The Jim Bolger-trained filly lost out in the Irish Oaks to Pat Smullen's mount, but responded with a win by a neck in Thursday's Group One event.
Ridden by Kevin Manning, the win was Bolger's first victory in the race since Lush Lashes in 2008.
French challenger Sea Calisi was a further neck away in third.
Manning, who pushed Pleascach on in the final furlong, said: "She battled all the way to the line and she's done it very well.
"I thought she was back to her best when I rode her work last week.
"She goes on various types of ground and is a very talented filly."
Bolger added: "Previously we tried to settle her a little bit and it meant breaking her stride and Kevin decided whatever happened he wasn't going to break her stride today. He gave her a beautiful ride
"We knew she was at the top of her game coming here."