Quick off the blocks
Bagnaia was quick off the mark to take the lead from Bastianini, who was starting on pole for the first time in his career but failed to finish due to a deflated front tyre.
There was further drama on the opening lap as Joan Mir, starting in eighth, crashed out at turn four – his sixth abandonment of the season, and the most of any rider.
Miller in mix
Miller temporarily took the lead from Bagnaia with 21 laps to go, but the Italian instantly hit back and his fifth triumph of the season – a personal record – was never in doubt.
But in what could yet prove a big moment in the championship battle, Quartararo produced a late rally to climb from an early sixth into an eventual second place.
Late charge
The reigning MotoGP world champion climbed above Miller, who held on for third, while Jorge Martin recovered slightly from a crash early on the final lap to finish 10th.
Quartararo did not quite have enough left to catch Bagnaia, however, with half a second separating the pair in the end to ensure the title battle remains alive and well.
Over to Misano
The MotoGP caravan now moves to the Misano World Circuit Marco Simoncelli for the San Marino Grand Prix to be held on on September 4.
RESULTS (TOP 10)
1. Francesco Bagnaia (Ducati)
2. Fabio Quartararo (Monster Energy Yamaha) +0.492 3. Jack Miller (Ducati) +2.163
4. Luca Marini (Mooney VR46) +8,348
5.Johann Zarco (Pramac Racing) +8.821
6. Alex Espargaro (Aprilia) +11,287
7. Brad Binder (Red Bull KTM) +11,642
8. Alex Rins (Suzuki Ecstar) +11,780
9. Marco Bezzecchi (Mooney VR46) +16,987
10.Jorge Martin (Pramac Racing) +17.144
STANDINGS
(Riders)
1. Fabio Quartararo (Monster Energy Yamaha) – 200
2. Aleix Espargaro (Aprilia) – 168
3. Francesco Bagnaia (Ducati) – 156
4.Johann Zarco (Pramac Racing) – 125
5. Jack Miller (Ducati) – 123
(teams)
1. Ducati-279
2. Aprilia Racing – 253
3. Monster Energy Yamaha – 226
4. Pramac Racing – 212
5. Red Bull KTM – 192