Renault had a good start to the evening - Nico Hulkenberg progressed in sixth, with Jolyon Palmer just behind in eighth.
Meanwhile, Carlos Sainz had a terrible end to the session, parking up before he completed his final flying lap, complaining of no power.
"Sorry for that," came the response from the pit wall - after he'd recorded the quickest first-sector time as well.
Pascal Wehrlein made his return for Sauber - and was sixth-tenths of a second quicker than his team-mate Marcus Ericsson, who was second in the drop-zone.
Kimi Raikkonen lost a bit of his car on his last attempt to record a quick time - but he was still third-quickest overall.
Mercedes' Lewis Hamilton topped the charts, having spent most of free practice pointing out how daft it is to try out cars and strategy for a night race during the daytime.
OUT: Carlos Sainz (Toro Rosso), Stoffel Vandoorne (McLaren), Sergio Perez (Force India), Marcus Ericsson (Sauber), Kevin Magnussen (Haas)
Williams got Lance Stroll out on track with only three minutes to go, not long enough for him to make a real bid for Q3 - but Felipe Massa did well, coming in eighth.
Fernando Alonso, down the way for McLaren, was nowhere to be seen - and was spotted with four minutes to go with his gear partially removed.
He explained afterwards that he had suffered a power-unit problem - something he's quite familiar with at this point.
Elsewhere, Haas's Romain Grosjean sang happy birthday to himself, two days prematurely, as he came in ninth.
At the top of the leaderboard, the Renaults had another utter stormer - Hulkenberg in fifth and Palmer in tenth. The Mercedes of Hamilton and Valtteri Bottas were split by 0.02 of a second, with the Ferraris of Sebastian Vettel and Kimi Raikkonen tucked behind them.
Read the full article on eurosport.co.uk: Bahrain Grand Prix qualifying: Maiden pole for Bottas, no power for Alonso