Ocon, who races in the DTM for Mercedes, but has also competed in two FP1 sessions for Renault this season, lapped in 1m 31.212s, which was around a second and a half quicker than he managed in the F1 W07 Hybrid on Tuesday.
The Frenchman completed 59 laps over the morning - a tally that was only bettered by Pascal Wehrlein, who continued Pirelli’s 2017 tyre development work with a further 61 laps in a 2014-spec Mercedes.
Ferrari's Kimi Raikkonen and Renault's Jolyon Palmer had each taken turns at the top of the standings, but were second and fourth respectively at the break, with Red Bull junior Pierre Gasly splitting them.
McLaren reserve Stoffel Vandoorne was back in action for the Woking-based team having taken over driving duties from Fernando Alonso, and was fifth at lunch, just ahead of Haas rookie Santino Ferrucci - the American enjoying his second day in the VF-16.
Fellow young drivers Nikita Mazepin and Sergio Sette Camara were seventh and eighth for Force India and Toro Rosso respectively, with the latter making his F1 test bow.
Completing the timesheet below Wehrlein were Williams' Valtteri Bottas and Manor's Jordan King, who managed the fewest laps of anyone in the morning.
Sauber are the only team not present.
You can follow minute-by-minute timing updates on the official F1 App - go to 'Results and Standings' and click 'Test'.
Unofficial Wednesday test times from Great Britain
|3||Pierre Gasly||Red Bull||1:33.404||2.192||45|
|7||Nikita Mazepin||Force India||1:34.553||3.341||31|
|8||Sergio Sette Camara||Toro Rosso||1:35.002||3.790||38|
|9||Pascal Wehrlein (PIRELLI)||Mercedes *||1:36.182||4.970||61|
* 2014-spec car