Lewis Hamilton bolted on the soft tyre and went fastest as the session approached the halfway mark, setting a 1min 06.390sec, but this was soon bettered by team-mate Bottas who posted time 0.004sec quicker.
Gasly then went faster as drivers pushed towards the 1min 05sec, but it was Verstappen who broke through with a 1min 05.910sec – this would ultimately end as best time of the session.
Perez dipped a left rear wheel on the exit of Turn Four and span, as the Mexican struggled to set a fast time on the soft compound.
Drivers continued to lay down the laps with the threat of rain looming for FP2. Fernando Alonso looked ever more comfortable in the Alpine as he set a 1min 06.519sec to go sixth-fastest, with team-mate Esteban Ocon half a tenth behind.
Quick times were rare in the second half of the session as both Verstappen and Hamilton went for long runs on their medium tyres.
Lando Norris attempted to set some hot laps towards the end, but saw three flying laps in a row deleted due to track limits.
Verstappen ended the session fastest, dark clouds shifting over the Styrian mountains as teams take a break before FP2 commences at 2pm.
— Formula 1 (@F1) June 25, 2021
With the threat of rain still hanging over the Red Bull Ring, teams again hit the track early in a bid to rack up laps.
Max Verstappen went fastest early on once more with a 1min 6.643sec, before being bested by Lewis Hamilton by almost three tenths. Fernando Alonso was 0.450sec behind them in third, before Sergio Perez went a fraction quicker than the Spaniard
As spots of rain began to fall, drivers started to lose grip and go off at Turn Three, Hamilton locking his right front hard tyre as he ran wide.
Carlos Sainz then span off at Turn Four in an echo of Perez’s FP1 off, raking gravel onto the track as he came back on.
Under-pressure Valtteri Bottas has looked reasonably strong so far in Styria, setting a time just less than a tenth off Verstappen as the session approached the quarter-way mark.
Teams then elected to do qualifying laps in case the rain rolled in proper. Lance Stroll hit the top of the timesheets 1min 06.079sec, before Sebastian Vettel immediately went going 0.15sec faster. Vettel was on medium tyres whilst all those around him were on softs.