Rider Robbie Hannam took the Kevin and Pam Hughes-trained galloper to the front and she never gave her opposition a look-in in the $50,000 event over 1400m.
Kevin Hughes said it was no fluke Hannam was able to find the front from her tricky starting spot in barrier 14.
They had a plan to take luck out of the equation and Emily Margaret did not let her trainers and jockey down.
"We thought we could just grind them all into the ground and that is what she did," Hughes said.
"She was very, very fit and was just too good on the day.
"I was very, very pleased with her and Robbie did a great job."
Saturday's win was Emily Margaret's second at listed level.
Her first came in the Canterbury Belle Stakes over 1200m at Riccarton in September.
That race and Saturday's race were the first two legs of the South Island Filly Of The Year series.
Hughes said he had not ruled out aiming his filly at a clean sweep of the series by contesting the third leg of the series over 1600m at Riccarton early next month.
Before then, Emily Margaret is likely to chase more black type for her pedigree page in the group 2 Wellington Guineas.
The Pins filly was given a hard run when failing in her first venture to Trentham for the group 3 Desert Gold Stakes.
That result meant Emily Margaret had failed in all three attempts over 1600m.
Hughes said he hoped his filly could see out the distance with a well-judged ride.
"I think 1400m is her pet distance," Hughes said.
"You might get away with a mile [1600m] as a 3yr-old.
"If she had someone like Robbie riding, she could steal a mile race, so we might do that third leg. We'll just see what happens at Wellington."
Runner-up Dreamtesta and third-placegetter Naval Fleet were both given brilliant rides and had few excuses for their defeats.
Rider Jason Laking gave North Island raider Naval Fleet a perfect run in the trail, but she simply could not keep pace with Emily Margaret in the home straight.
BB Hong had Dreamtesta in the one-one throughout and she ran home gamely to notch her second consecutive listed race second placing.
Claiming apprentice riders fought out the finish of both of the open handicap events at Wingatui on Saturday.
Disturbance backed up her fresh-up win at Riccarton last month to stay unbeaten this season in 1200m races.
The Shane Kennedy and Anna Furlong-trained mare, ridden by Kate Cowan, held out Johnny Jones and Tina Comignaghi by a neck.
Comignaghi went one better in Saturday's open 1600m event.
She rode Residential to win by a nose over Accidental Offside, ridden by Jasmine Fawcett.
