The durable Missunited made every yard of the running to win the Seamus & Rosemary McGrath Memorial Saval Beg Stakes at Leopardstown.
Trained by Mick Winters, the seven-year-old mare won the Galway Hurdle last summer and this display booked her place in the Ascot Gold Cup later in the month.
Ridden by Kevin Manning, she was challenged for the lead just before the home bend by Sir Ector but saw him off and then held off Shu Lewis by three-quarters of a length.
John Oxx's Tarana was third with 2-1 favourite Eye Of The Storm fourth.
"I think her stride is bigger this year. She seems to be pointing out her toe longer," said Winters.
"John Supple rode her in two pieces of work - in Patsy Byrnes' place - and he felt she was going well.
"Kevin rode a lovely even pace through the race.
"She'll go now for the Ascot Gold Cup."
Later on the card the Ger Lyons-trained Roheryn justified strong market support (16-1 into 17-2) to win the King George V Cup.