As had been the case in the morning, Mercedes' Nico Rosberg offered a plucky challenge to the Red Bulls.
On the medium compound tyre, Rosberg emerged with the honours, beating Webber by just 0.001 seconds.
Times were over a second faster on softs, and Vettel's early 1m25.722s secured the top spot with an hour to spare, as teams then switched to long-stint tyre work.
Webber repeated the practice one Red Bull symmetry by grabbing second, 0.289s slower than his team-mate, who is poised to secure a fourth consecutive Formula 1 title this weekend.
Following his morning gearbox issues, Alonso made up for lost time with 37 laps of running. His team-mate Felipe Massa was seventh.
Kimi Raikkonen got into the top 10 this time in eighth, but was half a second down on team-mate Grosjean.
The McLarens completed the top 10 spots.
Pastor Maldonado provided the most notable incident when his Williams shed a wheelnut on track. He managed to coax the loose-wheeled car back as far as the pitlane entry before having to park.
Paul di Resta was back in action for Force India after his earlier illness and took 15th place, 0.2s and three spots behind his team-mate Adrian Sutil.