Charles Leclerc once again set the early pace during the morning as he posted a best time of 1:34.366 in the Ferrari F1-75 to go a second quicker than the pretty in pink Alpine, with Esteban Ocon behind the wheel.
Max Verstappen was third for Red Bull on his first outing in Bahrain, whilst Yuki Tsuonda also climbed into the cockpit for the first time this week for AlphaTauri.
Testing will finish at 2pm local time for lunch before resuming at 3pm for another four hour afternoon session. Testing then concludes on Saturday. Meanwhile Haas will get two additional hours of running on each day following their freight issues earlier this week.