With the forecast rain clearing in the early hours of the morning, the field was greeted with mostly dry conditions for the opening 45-minute session.
The only exception were several isolated damp patches and small rivers left over from yesterday's flash flooding, while cold track temperatures also proved to be a challenge.
That left the times back in the 1m33s bracket in the early stages, Pol Espargaro leading the way with a 1m33.169s, set right before the Honda rider was forced to dodge a wallaby that scrambled across the track on the exit of Turn 4.
As conditions improved so did the times, Miguel Oliveira going fastest with a 1m32.494s before Fabio Quartararo took over with a 1m32.318s.
Espargaro was the first into the 1m31s before the quarter-hour mark with a 1m31.983s only for Marco Bezzecchi to lower the benchmark to a 1m31.582s a short time later.
Quartararo then took over with a pair of session-best lap, the second a 1m31.362s that left him just over two-tenths clear of the field.
The next improvement near the front came 10 minutes later, Marc Marquez closing the gap to four-hundredths as he moved into second place.
A lap later he bumped Quartararo off top spot, a 1m31.258s moving the Honda rider a tenth clear of his Yamaha rival.
After a brief trip to the pits for a front fork change Marquez continued his charge, blowing the gap back to Quartararo out to more than four tenths with a 1m30.897s.
At that point Espargaro made it a Repsol Honda one-two as he jumped into second place with two near identical laps that left him just under three tenths behind his teammate.
With four minutes to go Miller fired to the top of the times with a 1m30.561s, before improving to a 1m30.459s on his next run.
However his hopes of some early hometown heroics were dashed when Zarco set a 1m30.368s right at the flag to pip Miller by nine-hundredths.
Green tyre runs at the end of the session saw Alex Marquez move up to third ahead of Alex Rins, Aleix Espargaro and Enea Bastianini.
Marc Marquez, meanwhile, spent the final 10 minutes of the session trialling a new aero package, which features rear seat wings, and slipped back to seventh.
Francesco Bagnaia made a slow start to the weekend, a quiet showing in the first practice session leaving him eighth fastest.
Fabio Di Giannantonio and Bezzecchi were next while Pol Espargaro made little progress on his early pace and ended up 11th, one place clear of Quartararo.
Practice for the Australian Grand Prix continues at 2:10pm local time.
2022 Australian MotoGP Free Practice 1 results
| Cla | # | Rider | Bike | Time | Gap | Interval |
|---|---|---|---|---|---|---|
| 1 | 5 |  Johann Zarco |
Ducati | 1'30.368 | ||
| 2 | 43 |  Jack Miller |
Ducati | 1'30.459 | 0.091 | 0.091 |
| 3 | 73 |  Alex Marquez |
Honda | 1'30.493 | 0.125 | 0.034 |
| 4 | 42 | Alex Rins |
Suzuki | 1'30.511 | 0.143 | 0.018 |
| 5 | 41 | Aleix Espargaro |
Aprilia | 1'30.687 | 0.319 | 0.176 |
| 6 | 23 |  Enea Bastianini |
Ducati | 1'30.790 | 0.422 | 0.103 |
| 7 | 93 | Marc Marquez |
Honda | 1'30.897 | 0.529 | 0.107 |
| 8 | 63 | Francesco Bagnaia |
Ducati | 1'31.077 | 0.709 | 0.180 |
| 9 | 49 | Fabio Di Giannantonio |
Ducati | 1'31.087 | 0.719 | 0.010 |
| 10 | 72 | Marco Bezzecchi |
Ducati | 1'31.166 | 0.798 | 0.079 |
| 11 | 44 | Pol Espargaro |
Honda | 1'31.194 | 0.826 | 0.028 |
| 12 | 20 | Fabio Quartararo |
Yamaha | 1'31.195 | 0.827 | 0.001 |
| 13 | 89 | Jorge Martin |
Ducati | 1'31.419 | 1.051 | 0.224 |
| 14 | 12 | Maverick Viñales |
Aprilia | 1'31.436 | 1.068 | 0.017 |
| 15 | 36 | Joan Mir |
Suzuki | 1'31.531 | 1.163 | 0.095 |
| 16 | 40 |  Darryn Binder |
Yamaha | 1'31.700 | 1.332 | 0.169 |
| 17 | 35 |  Cal Crutchlow |
Yamaha | 1'31.868 | 1.500 | 0.168 |
| 18 | 88 |  Miguel Oliveira |
KTM | 1'31.950 | 1.582 | 0.082 |
| 19 | 21 | Franco Morbidelli |
Yamaha | 1'32.178 | 1.810 | 0.228 |
| 20 | 87 | Remy Gardner |
KTM | 1'32.207 | 1.839 | 0.029 |
| 21 | 33 | Brad Binder |
KTM | 1'32.566 | 2.198 | 0.359 |
| 22 | 10 | Luca Marini |
Ducati | 1'32.831 | 2.463 | 0.265 |
| 23 | 25 | Raúl Fernández |
KTM | 1'32.947 | 2.579 | 0.116 |
| 24 | 45 |  Tetsuta Nagashima |
Honda | 1'34.437 | 4.069 | 1.490 |
| View full results | ||||||
