Just before her win, her sister, racehorse trainer Emmalee Browne, notched an impressive win with Desperaux at Ellerslie.
Twelve started the World Cup class, the third in the NZ series, with nine coming back for the second round. McVean, Maurice Beatson on My Gollywog and Bernard Denton on Suzuki were the only ones clear.
McVean's clear and speedy 50.05 seconds couldn't be matched, although second placed Beatson gave it a pretty good shot, paying for his efforts with two rails.
Denton also took two rails. In fourth place was Danielle Maurer aboard Blue Rinse in their first World Cup start.
McVean had a slender one-point advantage over Beatson going into the class, and while she'll still be ahead, the series is turning into a two-horse race between the World Champs team-mates.
Clear rounds were scant in the young rider class too, which saw just Tim Myers on Pick Me NZPH and Luke Dee on Ombudsman the only two from the 10-strong field coming back for the jump-off.
Dee was out first and took a rail as he tried to lay a challenge for Myers, who took the class with a double clear.
In the pony grand prix Rebecca Porter and the perennial Chobidong were the only ones to go clear and inside time. Until last weekend the combination had never won a grand prix -now they are sitting on a hat trick.
Second-placed Emily Fraser and Tony the Pony were clear but had a single time fault.
And it was all Lisa Hogg and IQ in the junior rider where they too were the only clear round.
Bomac World Cup (third round of NZ series): Katie McVean (Mystery Creek) Dunstan Daffodil 1, Maurice Beatson (Dannevirke) My Gollywog 2, Bernard Denton (Gisborne) Suzuki 3, Danielle Maurer (Auckland) Blue Rinse 4, Susie Hayward (Ashburton) Andretti 5, Lisa Coupe (Kumeu) Bates Amaretto MVNZ 6.
Giltrap Audi young rider: Tim Myers (Taranaki) Pick Me NZPH 1, Luke Dee (Gisborne) Ombudsman 2, Mathew Dickey (Taranaki) Kiwi Guard 3, Rachael Bentall (Hastings) Kiwi Brave 4, Mathew Dickey (Taranaki) Witzcellar 5, Natasha Brooks (Cambridge) Uranda 6.
JLT Bloodstock pony grand prix: Rebecca Porter (Hastings) Chobidong 1, Emily Fraser (Dannevirke) Tony the Pony 2, Nakeysha Lammers (Northland) Airborne Magic 3, Emily Fraser (Dannevirke) Tiger Tale LS 4, Melanie Weal (Te Awamutu) Hopeful Illusion 5, Morgan Percy (Taranaki) Surprise Illusion 6.
Cushionride seven year old: Philip Steiner (Tauranga) Annandale Karla K 1, Katie McVean (Mystery Creek) Dunstan Kiwi Iron Mark 2, Katie McVean (Mystery Creek) Dunstan Delilah 3, Katie McVean (Mystery Creek) Dunstan Springfield 4, Maurice Beatson (Dannevirke) Johnny Castle 5, Sally Steiner (Tauranga) Annandale Baby Doll 6.
KiwiSpan junior rider: Lisa Hogg (Ohope) IQ 1, Natasha Brooks (Cambridge) Waitangi Jet Stream 2, Henry Booth (Manawatu) Getmshorty 3, Melanie Weal (Te Awamutu) Cross Your Heart 4, Megan Webb (Hunterville) Abernaki Chief 5, Logan Massie (Dannevirke) Kiwi Ludo 6.
Iverquantel amateur rider: Merran Hain (Gisborne) Untouchable 1, Brooke Zander (Waipukurau) Double J Rumours 2, Rebecca Presow (Eketahuna) La Bella Vida 3, Sandra Warren (Feilding) Candy Bear 4, Shari Johnstone (Bulls) My Turtle 5, Pip McCarroll (Waikanae) Kabo Lunar 6.
STH pro amateur rider: Chloe Akers (Opiki) Kiwi Motto 1, Caroline Tatere (Dannevirke) Grader 2, Amanda Howie (Hunterville) Obeone Kanobe 3, Ali McWatters (Wellington) Willowridge Eclipse 4, Rachel Moore (Hastings) Navy Blue 5, Chloe Akers (Opiki) HR Khemosabi 6.