Zane Goddard has set the pace after three hours of official pre-season testing at Queensland Raceway.
The Matt Stone Racing driver set a 1:09.0257s flyer on his 16th lap, which held sway over the field to midday.
The 21-year-old's time was just 0.0061s quicker than Anton De Pasquale, who set a 1:09.0318s on his 24th lap of the day.
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De Pasquale completed 45 laps to midday in his #100 Dick Johnson Racing Ford Mustang.
Teammate and fellow DJR recruit Will Davison logged 25 laps in the #17 entry, and was three tenths down on De Pasquale.
Red Bull Ampol Racing duo Jamie Whincup and Shane van Gisbergen were fourth and fifth, with MSR's Jake Kostecki slotting into third.
Whincup set his fastest lap of the morning, a 1:09.1803s, on his fourth lap of the day.
In his second stint behind the wheel of the #97 Commodore, Garth Tander had a big lock-up on approach to Turn 4 and fired off.
The car wasn't damaged, and Tander safely returned to pit lane.
Team Sydney duo Fabian Coulthard and Garry Jacobson also turned laps, with Jonathon Webb also getting behind the wheel of the #19 Local Legends entry.
Testing at Ipswich will conclude at 1700 AEST.
Victorian teams will hit Winton Motor Raceway on Tuesday.
The 2021 Repco Supercars Championship will commence at the Repco Mt Panorama 500. Tickets are on sale now.