Raced over a course involving a 400m sea swim, 20km bike and 4km run, Grant trailed early leader Emma Rathbone from the water by 45sec.
But a speedy and efficient transition to the bike saw Grant first away and she opened up a 2min lead over Kate Menzies, who had moved into second place by the completion of the run.
Grant cruised to victory 2min 38sec clear of Menzies in 1hr 6min 2sec, with Kerry Rowley's late charge not enough as she finished 13sec adrift of Menzies (1hr 8min 53sec).
The race served as a confidence builder for Grant, who missed last season through a stress fracture following her fourth place in the junior women's section at the world championships in Hamburg, Germany.
Grant (20), a first year applied sciences and bachelor of arts student, spent the winter months conditioning and building a base for her first year in the competitive ranks of the open and under-23 grades.
It may have come four months early, but Glen McSkimming received an early 40th birthday gift with victory over the national 40-44 age-group champion Ian Paulin.
McSkimming will not turn 40 until next April, but as ages are taken as at December 31, 2009, he will have to compete as a 40-year-old as of January 1.
The two had checked each other out over the past week to confirm each other's entry into yesterday's event, and it appeared early on that first blood would go Paulin's way when he held a 62sec lead on McSkimming following the swimming stage.
Midway through the cycle stage, McSkimming had halved this lead and just nudged ahead coming through transition to the run where he was able to hold Paulin out to clinch the race title in 1hr 0min 1sec, with Paulin second, 34sec behind.
Steve Colpitts was third in 1hr 5min 16sec.
The associated half distance event announced the arrival of Mary Gray, a rising talent on the local triathlon scene.
Gray (14), a year 9 pupil at Otago Girls High School, led the combined field from the swim and was the fastest competitor on the run stage.
But she faltered on the bike stage, in the windy conditions, and was overtaken by eventual overall winner Paul Woods, who battled to hold Gray out over the closing stages of the run. Woods finished the course in 40min 11sec and Gray second in 40min 22sec. Third was Deborah Bowler in 53min 34sec.
