Max Chilton led the way in free practice for GP2's standalone Sakhir races on Friday morning.
The GP2 field has stayed at the circuit following last weekend's Bahrain Grand Prix support event, with rounds five and six the series' only races away from the Formula 1 bill in 2012.
Chilton led the way for most of the half-hour session, heading his team-mate Rio Haryanto in a Carlin one-two for a while.
Haryanto was ultimately pushed back to fourth as championship leader Davide Valsecchi (DAMS) moved up to second - although last weekend's double winner was still 0.3 seconds off Chilton's 1m42.136s benchmark.
Valsecchi's title rival Luiz Razia took third for Arden, with Caterham's Giedo van der Garde behind Haryanto in fifth.
Fabio Leimer (Racing Engineering), Felipe Nasr (DAMS), Marcus Ericsson (iSport), Brendon Hartley (Ocean) and Fabrizio Crestini (Lazarus) completed the top 10.
The session's only incident was a brief red flag after Jolyon Palmer's iSport car stopped at Turn 10.
With the field having raced at Sakhir just a few days ago and amid expectations that tyre wear will be a critical factor this weekend, most drivers only completed a handful of laps, and Lotus duo Esteban Gutierrez and James Calado did not run beyond installation laps.
Qualifying and the feature race both take place later on Friday in the compact schedule, with the sprint race on Saturday afternoon.
Pos Driver Team Time Gap 1. Max Chilton Carlin 1m42.136s 2. Davide Valsecchi DAMS 1m42.436s + 0.300s 3. Luiz Razia Arden 1m42.691s + 0.555s 4. Rio Haryanto Carlin 1m42.793s + 0.657s 5. Giedo van der Garde Caterham 1m42.883s + 0.747s 6. Fabio Leimer Racing Engineering 1m42.947s + 0.811s 7. Felipe Nasr DAMS 1m43.008s + 0.872s 8. Marcus Ericsson iSport 1m43.051s + 0.915s 9. Brendon Hartley Ocean 1m43.076s + 0.940s 10. Fabrizio Crestani Lazarus 1m43.109s + 0.973s 11. Nathanael Berthon Racing Engineering 1m43.193s + 1.057s 12. Stefano Coletti Coloni 1m43.277s + 1.141s 13. Fabio Onidi Coloni 1m43.283s + 1.147s 14. Rodolfo Gonzalez Caterham 1m43.311s + 1.175s 15. Dani Clos Addax 1m43.405s + 1.269s 16. Simon Trummer Arden 1m43.522s + 1.386s 17. Nigel Melker Ocean 1m43.573s + 1.437s 18. Tom Dillmann Rapax 1m43.852s + 1.716s 19. Giancarlo Serenelli Lazarus 1m44.613s + 2.477s 20. Johnny Cecotto Addax 1m45.449s + 3.313s 21. Stephane Richelmi Trident 1m46.271s + 4.135s 22. Jolyon Palmer iSport 1m53.449s + 11.313s 23. Julian Leal Trident 1m57.225s + 15.089s 24. Esteban Gutierrez Lotus 25. James Calado Lotus 26. Ricardo Teixeira Rapax