The #1 Arise Racing Ferrari 296 topped the first of two 20-minute qualifying sessions, clocking a 2:00.9861s at the death.
Melbourne Performance Centre’s Brendon Leitch in the #7 Audi R8 was the first driver to do a 2:01s in the session, which stood as the pole time until Mostert’s last-gasp effort.
With a 2:01.8311s, the Lamborghini Super Trofeo Europe champion wound up 0.8450s adrift of the leading Ferrari.
The sister Arise Racing entry of Jaxon Evans was third, one second away from Mostert.
Team BRM driver Alex Peroni was fourth and Supercars points leader Will Brown was fifth in the second of the Melbourne Performance Centre Audis.
Jayden Ojeda (Tigani Motorsport), Alex Fontana (Car Collection Motorsport), Brendon Grove (Grove Racing), Declan Fraser (Triple Eight Race Engineering), and Garth Walder (GWR Australia) completed the top 10.
Mostert’s teammate Liam Talbot sealed back-to-back pole positions with a 2:02.9181s, beating Paul Stokell in the #181 Audi R8 he’ll share with Renee Gracie by three tenths of a second.
Hometown hero Brad Schumacher was third and half a second off Talbot’s pace in the car he’ll share with Brown.
Sergio Pires in the Valmont Racing Audi R8 was fourth ahead of the Elliott Schutte/Jaxon Evans Ferrari in fifth.
Mark Rosser (Team BRM), Tim Miles (Melbourne Performance Centre), Peter Hackett (Triple Eight Race Engineering), Stephen Grove (Grove Racing), and Theo Koundouris completed the top 10.
Mostert and Talbot hold a 30-point advantage over Brown and Schumacher in the GT World Challenge Australia standings.
Race 1 of the weekend gets underway at 12:45pm AEDT on Saturday with coverage live and exclusive to the Seven Network. Race 2 of the weekend takes place at 2:55pm on Sunday.
Monochrome GT4 Australia
Lochie Dalton was the star performer in Qualifying 1 for Monochrome GT4 Australia. Driving the Buckby Motorsport Mercedes-AMG GT4, the former Super2 driver was two tenths quicker than Gomersall Motorsport’s Aaron Seton.
Dalton set a 2:13.1766s at Mount Panorama in cool conditions on Saturday morning.
George Miedecke in the Miedecke Motorsport Ford Mustang was third with the first Porsche 718 Cayman of Lachlan Mineeff in fourth and Ryder Quinn fifth in his BMW M4.
Miedecke’s co-driver Rylan Gray topped Qualifying 2 ahead of Marcos Flack’s teammate Tom Hayman. Jake Camilleri was sixth and third across the two sessions.
Daniel Jilesen was fourth in the TekworkX Motorsport Porsche he’ll share with Zoe Woods while Cody Burcher was fifth in the Tim Leahey BMW M4.
Race 1 gets underway at 4:45pm AEDT on Saturday. Race 2 is scheduled for 10:50am AEDT on Sunday.