Williams could threaten Mercedes' qualifying domination so far this season following a superb conclusion to practice ahead of the Austrian Grand Prix.
The Grove-based marque have been edging closer to Mercedes in recent races, but without the results their performances have deserved due to a range of issues.
But at the Red Bull Ring where Formula One is back after an 11-year absence, Valtteri Bottas and Felipe Massa finished first and third at the end of the final hour-long session.
Bottas knocked Lewis Hamilton off top spot in the closing stages with a lap time of one minute 09.848secs.
The Briton, however, still has the best time to his name so far this weekend with a 1:09.542 in FP2 on Friday.
Hamilton finished 0.050secs adrift in FP3, with Massa only three thousandths of a second further behind to suggest Williams will at least give the Mercedes duo of Hamilton and team-mate Nico Rosberg a run for their money in qualifying.
Championship leader Rosberg had to settle for fifth on the timesheet, 0.151secs behind Bottas, with Toro Rosso's Daniil Kvyat a surprise name in fourth following a lap of 1:09.927.
Ferrari's Fernando Alonso, third best in both 90-minute sessions on Friday behind the Mercedes pairing, was again in close attendance, just two tenths of a second off the pace.
Beyond the leading six, however, there was a gap, with Canadian GP winner Daniel Ricciardo half-a-second down in his Red Bull, with team-mate Sebastian Vettel just scraping into the top 10.
Sandwiched in between the Red Bulls were McLaren's Kevin Magnussen and Kimi Raikkonen in his Ferrari, the Finn at least showing some degree of improvement after a miserable Friday.
At the bottom of the timesheet due to technical issues were the other two Britons in Marussia's Max Chilton and McLaren's Jenson Button.
It was a wretched session for Button, in particular, who managed just four laps after complaining of a lack of engine braking early in the session, leaving his mechanics with a race to find a cure ahead of qualifying, notably as the right-rear brake caught fire on his return to the pits.
With 10 minutes remaining Marussia confirmed Chilton was confined to the garage due to an unspecified problem with his car.
Chilton finished three seconds off the pace as he was unable to set a time on the supersoft tyres, whilst Button was 4.4secs back.