The Prema Racing driver lined up sixth, making up a place on the first lap before an early safety car.
He was then able to capitalise on contact between poleman Gregoire Saucy (ART) and his team-mate Paul Aron to move into the podium places.
The 2021 Aston Martin Autosport BRDC Young Driver of the Year was then able to pass fellow Prema driver Dino Beganovic for second on lap 14, before taking the lead from championship leader Gabriel Bortoleto the following tour.
Despite a very close final lap fight between Williams Academy member O’Sullivan, Bortoleto, Franco Colapinto (MP Motorsport), Hitech driver Sebastian Montoya and Caio Collet (VAR), it was O’Sullivan who emerged victorious.
Bortoleto held on for second for Trident, with Collet taking the final podium place after contact between Montoya and Colapinto at Turn 6 saw the Red Bull junior shoot across the gravel, falling to 10th, while Colapinto finished fourth.
Saucy lined up on pole for Sunday’s race, which took place in far drier conditions than Saturday’s mixed action.
Despite Williams juniors O’Sullivan and Colapinto making brief contact at Turn 3, the pair continued, before the safety car was deployed as Gabriele Mini (Hitech) ran off at Turn 4.
The Alpine Academy member became beached after contact with the rear of Luke Browning (Hitech), who was forced to pit with a puncture.
Racing resumed on lap five, with Saucy getting a good jump on the rest of the field, while further back Collet and Kaylen Frederick (ART) tussled for seventh.
Beganovic, who started second, closed on Saucy out front before making the move at Turn 4 on lap seven to take control of the race.
But the Prema driver began to struggle with his tyres, allowing the pack to close, before Saucy and Aron made contact at Turn 4, the latter’s front wing handing the Frenchman a puncture and dropping both out of contention.
Bortoleto, who had inherited second, then took the lead on lap 13 at Turn 4, before Beganovic fell to third as O’Sullivan moved into second place next time round.
O’Sullivan closed on Bortoleto before taking the lead himself on lap 15, with Colapinto moving into third at Turn 4 the following lap as Beganovic’s tyre woes continued, with Collet also passing him on lap 18.
Montoya then also passed the Swede, taking fifth at Turn 7 on lap 18 despite a brief foray onto the gravel, taking fourth several laps later from Collet.
But it was a similar move at Turn 6 on the final lap which saw Montoya’s race ruined, making contact with Colapinto to see both fall out of the podium places. Collet profited for third, with Colapinto fourth ahead of Beganovic.
Jonny Edgar finished sixth for MP Motorsport, with Campos Racing pair Christian Mansell and Hugh Barter in seventh and eighth.
Sophia Floersch had scored her first points of the year for PHM Racing by Charouz in ninth, with Montoya in 10th after his last-lap off. But Floersch was disqualified for a technical infringement post-race, while Montoya was given a 10-second penalty for the clash with Colopinto, lifting Pepe Marti to ninth and Leonardo Fornaroli into the final points place.
F3 Austria - Feature race results
| Cla | Driver | Team | Laps | Gap | Interval |
|---|---|---|---|---|---|
| 1 |
 Zak O'Sullivan |
 Prema Powerteam |
26 | ||
| 2 | Gabriel Bortoleto | Trident |
26 | 0.844 | 0.844 |
| 3 |
 Caio Collet |
 Van Amersfoort Racing |
26 | 1.696 | 0.852 |
| 4 |
 Franco Colapinto |
MP Motorsport |
26 | 2.458 | 0.762 |
| 5 | Dino Beganovic | Prema Powerteam |
26 | 4.460 | 2.002 |
| 6 |
Jonny Edgar |
MP Motorsport |
26 | 4.723 | 0.263 |
| 7 | Christian Mansell |  Campos Racing |
26 | 5.296 | 0.573 |
| 8 | Hugh Barter | Campos Racing |
26 | 5.676 | 0.380 |
 Sophia Flörsch |
PHM Racing by Charouz | 26 | 6.230 | 0.554 | |
| 9 | Pepe Martí | Campos Racing |
26 | 9.530 | 3.300 |
| 10 | Leonardo Fornaroli | Trident |
26 | 10.624 | 1.094 |
| 11 | Oliver Goethe | Trident |
26 | 12.441 | 1.817 |
| 12 | Taylor Barnard |  Jenzer Motorsport |
26 | 13.883 | 1.442 |
| 13 | Nikita Bedrin | Jenzer Motorsport |
26 | 14.601 | 0.718 |
| 14 | Oliver Gray | Rodin Carlin | 26 | 15.148 | 0.547 |
| 15 |
 Rafael Villagomez |
Van Amersfoort Racing |
26 | 15.803 | 0.655 |
| 16 | Nikola Tsolov |  ART Grand Prix |
26 | 16.236 | 0.433 |
| 17 | McKenzy Cresswell | PHM Racing by Charouz | 26 | 16.584 | 0.348 |
| 18 | Tommy Smith | Van Amersfoort Racing |
26 | 16.921 | 0.337 |
| 19 | Roberto Faria | PHM Racing by Charouz | 26 | 17.355 | 0.434 |
| 20 |
 Sebastian Montoya |
Hitech Pulse-Eight | 26 | 18.814 | 1.459 |
| 21 | Hunter Yeany | Rodin Carlin | 26 | 23.510 | 4.696 |
| 22 | Luke Browning | Hitech Pulse-Eight | 26 | 38.170 | 14.660 |
| 23 | Alex Garcia | Jenzer Motorsport |
26 | 53.151 | 14.981 |
| 24 | Mari Boya | MP Motorsport |
26 | 53.750 | 0.599 |
| 25 | Paul Aron | Prema Powerteam |
26 | 1'06.265 | 12.515 |
| 26 |
 Kaylen Frederick |
ART Grand Prix |
26 | 1'07.566 | 1.301 |
| 27 |
Gregoire Saucy |
ART Grand Prix |
24 | 2 Laps | 2 Laps |
 Ido Cohen |
Rodin Carlin | 14 | 12 Laps | 10 Laps | |
| Gabriele Minì | Hitech Pulse-Eight | 0 | |||
| View full results | |||||
