Quartararo fired in a late 1m32.081s to outpace nearest rival Maverick Vinales by 0.356s, with only three other riders managing to lap within a second of the Frenchman.
The top three in both of Friday’s practice session – Vinales, Quartararo and Marc Marquez – reassumed their usual positions at the sharp end from the get go in FP3, with the Honda man setting a 1m33.051s to lead Vinales by three hundredths and Quartararo by a tenth.
Quartararo improved to within 0.052s of Marquez early in the second half of the session, and Vinales was then up on the reigning champion’s time after three sectors on two separate occasions, but Marquez’s laptime held out until the final minutes.
Vinales then used a fresh pair of soft tires to put together a 1m32.437s, going six tenths clear in FP3 and overhauling his own benchmark from Friday.
However, Quartararo responded immediately with an effort just under a tenth quicker, before lowering the benchmark further still with his next attempt and making sure of the top spot.
Behind the two Yamahas, Pol Espargaro was a standout third for KTM, seeing off Marquez by less than half a tenth despite the championship leader improving at the end.
Quartararo’s teammate Franco Morbidelli shot up to fifth at the checkered flag, leading LCR Honda’s Takaaki Nakagami and Valentino Rossi, who made it four Yamahas in the top seven.
Suzuki’s Alex Rins faced a potential battle through Q1, but managed to fight his way into the top 10 at the last moment, taking eighth ahead of the two Ducatis of wildcard Michele Pirro and Andrea Dovizioso.
Rins’ last-gasp heroics denied KTM’s Johann Zarco a spot in Q2, the Frenchman missing out by just 0.033s – with Tech 3’s Miguel Oliveira only another half a tenth down despite nursing a shoulder injury after his collision with Zarco at Silverstone.
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LCR Honda’s Cal Crutchlow, Pramac Ducati’s Jack Miller and works Ducati rider Danilo Petrucci were among the biggest names to miss out on an automatic Q2 spot.
Also missing out was Jorge Lorenzo in 19th, the three-time champion’s FP3 compromised by an apparent problem that manifested itself in the front wheel getting sideways and locking up on the straight.
Aprilia’s Andrea Iannone was 22nd, having suffered his second crash of the weekend at the turn 4 right-hander.