Mercedes-engined cars picked up where they left off after last week's four-day test at the Sakhir circuit, locking out the top three spots on the timesheet, while reigning champion Red Bull showed signs of improvement after a torrid pre-season so far.
Daniel Ricciardo set the fastest lap by a Renault-powered car so far to go fifth quickest, but the RB10 spent plenty of time in the garage being cut, hammered and fettled in between runs.
Bahrain F1 test photo gallery
Perez's 1m35.290s best lap was more than a second clear of Nico Rosberg's Mercedes, which set the fastest time overall of last week's test.
The German clocked over 60 laps this morning, comfortably more than any other driver, and lapped over a second faster than Kevin Magnussen's McLaren, which was third quickest.
Adrian Sutil enjoyed a far more productive start than he managed in last week's test, where a chassis problem all but eliminated his final day of running.
The German managed 31 laps and wound up less than half a tenth behind Magnussen.
Ferrari completed another quiet morning in Bahrain, managing only 12 laps with Kimi Raikkonen at the wheel. The 2007 world champion crashed in the closing stages of last week's test and the Scuderia has yet to complete a race run with the F14 T.
Pastor Maldonado brought the first part of the session to an early halt when the 'twin-tusk' Lotus E22 stopped at Turn 8. Caterham's Kamui Kobayashi was responsible for the only other red flag so far today, when he stopped early on with technical problems in the CT05.
Marussia appeared to overcome the IT problems that plagued it last week, as Max Chilton completed 16 laps and set the 10th fastest time, just half a second adrift of Maldonado's Lotus.
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