Racing Point's Sergio Perez was the surprise name at the top of the order in opening practice for the Styrian Grand Prix.
Red Bull driver Max Verstappen finished second, with the Mercedes duo of Valtteri Bottas and Lewis Hamilton third and fourth respectively.
Formula One is racing at Austria's Red Bull Ring for a second consecutive week following last Sunday's season opener.
Mercedes dominated the first race of the campaign at the same venue – topping all three practice sessions and qualifying before Bottas took the chequered flag.
But the all-black cars were knocked off the summit by both Perez and Verstappen at a sweltering Spielberg on Friday.
Perez finished 0.096 seconds clear of Verstappen with championship leader Bottas two tenths off the pace. Hamilton ended the opening running 0.253 sec slower than Perez.
Lance Stroll was fifth for Racing Point – whose car is modelled on the championship-winning Mercedes of last term – while Red Bull's Alexander Albon finished sixth.
Ferrari have brought a series of upgrades to this week's race, but the struggling Italian team continued to be off the pace.
Sebastian Vettel was only 10th, 0.903 sec slower than Perez's best lap, with team-mate Charles Leclerc further back in 12th.
Lando Norris, who last week became the youngest British driver to finish on a Formula One podium, was 14th for McLaren.
British driver Jack Aitken, deputising for Williams' George Russell, finished 17th of the 20 runners in his maiden grand prix outing. Russell will return to the cockpit this afternoon.
In the other Williams, Nicholas Latifi completed just six laps after a technical failure curtailed his running.
