Nico Rosberg replaced Lewis Hamilton as the man to beat on the soft tyres while his team-mate struggling to put it together in Prac Three.
Hamilton had been leading the way on the medium tyres, however, a swap to the softs saw Rosberg come to the fore.
The German driver clocked a 1:29.375 to set the fastest time of the weekend to date.
Hamilton tried to fight back but had a slow middle sector and ran off at Turn 9 - as many did - and eventually finished fourth, 1.544s down.
Jenson Button was second fastest for McLaren by was a staggering 1.391s slower than Rosberg while Alonso was third, a further 0.110s off the pace.
Daniel Ricciardo was fifth quickest for Red Bull in another solid morning while his team-mate Sebastian Vettel could only manage 12th.
Like many out in the final ten minutes, Vettel was caught up by a tail wind at Turn 9 that buffered his car and went him running wide.
Nico Hulkenberg had a good morning, bringing his Force India home in sixth place ahead of Kimi Raikkonen, Kevin Magnussen and Sergio Perez.
Felipe Massa completed the top ten on a mixed morning for Williams. While he put in 20 laps, team-mate Valtteri Bottas managed just two with his FW36 in need of a gearbox change.
As for Friday's troubled teams, Caterham seemed to get it right, both drivers running although neither particularly quick, but it was a mixed morning for Lotus.
Pastor Maldonado was able to put in the laps, cover 15 with a best time of a 1:34.754, however, Romain Grosjean did not.
On his first lap he reported a misfire, saying "unbelievable", which sent him back into the pits. Out 30 minutes later, he was heard yelling "nothing is solved" in sheer frustration. He did just three laps.
01 Nico Rosberg Mercedes 1:29.375 15 laps
02 Jenson Button McLaren 1:30.766 +1.391 20 laps
03 Fernando Alonso Ferrari 1:30.876 +1.501 11 laps
04 Lewis Hamilton Mercedes 1:30.919 +1.544 13 laps
05 Daniel Ricciardo Red Bull 1:30.970 +1.595 13 laps
06 Nico Hulkenberg Force India 1:30.978 +1.603 16 laps
07 Kimi Raikkonen Ferrari 1:31.156 +1.781 12 laps
08 Kevin Magnussen McLaren 1:31.251 +1.876 22 laps
09 Sergio Perez Force India 1:31.665 +2.290 17 laps
10 Felipe Massa Williams 1:31.723 +2.348 20 laps
11 Daniil Kvyat Toro Rosso 1:31.925 +2.550 17 laps
12 Sebastian Vettel Red Bull 1:32.255 +2.880 14 laps
13 Jean-Eric Vergne Toro Rosso 1:32.417 +3.042 16 laps
14 Jules Bianchi Marussia 1:34.184 +4.809 15 laps
15 Adrian Sutil Sauber 1:34.188 +4.813 16 laps
16 Kamui Kobayashi Caterham 1:34.413 +5.038 19 laps
17 Max Chilton Marussia 1:34.717 +5.342 15 laps
18 Pastor Maldonado Lotus 1:34.754 +5.379 15 laps
19 Marcus Ericsson Caterham 1:36.159 +6.784 21 laps
Romain Grosjean Lotus No time 4 laps
Esteban Gutierrez Sauber No time 2 laps
Valtteri Bottas Williams No time 2 laps