Despite Sebastian Vettel looking likely to take yet another pole position this season Mercedes AMG F1 turned things around as defending champion Lewis Hamilton took pole position with teammate Valtteri Bottas a very close second for the Spanish Grand Prix.
Alonso secured McLaren's first Q3 appearance of the season with a solid last lap to knock out teammate Stoffel Vandoorne by a little over 0.2s, with Pierre Gasly also dropping out in 12th, 0.1s further back from the second McLaren.
Both Ferrari's used the soft compound tyre for the second and final run in Q3, with the delta between soft and supersoft proving to be insignificant.
In Q2, the Big 3 teams all set their lap times on soft tires, thus ensuring that they were all starting on the same tires. Bottas qualified second, 0.040 seconds adrift of Hamilton.
Hamilton, the World Championship leader headed the Red Bull pairing after a closely-contested session.
Bottas was a shade faster than Hamilton in the first and third sectors, but Hamilton's mighty pace in the second sector meant the Finn ended up second-best. That's largely down to the tyres being two steps softer than in 2017, but also a reflection of the relentless development race in F1 - Hamilton's time was also a second quicker than the best lap in winter testing.
The two home favourites, Fernando Alonso and Carlos Sainz, gave the Spaniards something to cheer in eighth and ninth.
Sauber driver Charles Leclerc managed to split the Force Indias with a lap of 1m18.910s, nearly two-tenths faster than 15th-placed Sergio Perez.
Nico Hulkenberg reported a problem, suspected to be a fuel pressure issue, on his Renault and was able to complete only one representative lap - and it was insufficient for him to escape from Q1. He foresaw an "interesting race" on Sunday. His time was only good enough for 16th.
Those who feel that the current driver line up of Lance Stroll and Sergey Sirotkin is the worst in the team's history, could have their case strengthened this weekend.
Stroll was even slower, and crashed out during the closing stages, having run wide through Turn 12, a movement that sucked him through the gravel.