Mark Webber led Red Bull teammate Sebastian Vettel in a 1-2 finish on Friday in the opening session of Spanish Grand Prix practice.
Webber set a quickest lap time of 1 minute, 25.142 seconds at the Catalunya Circuit. The Australian driver is vying for his first victory of the season and second straight win in Barcelona.
Vettel, who has won three of the season's first four races, was just more than one-second behind Webber.
The defending F1 champion was two-tenths faster than Mercedes driver Nico Rosberg, while Ferrari driver Fernando Alonso was fourth in front of his home fans.
Mexican driver Sergio Perez was fifth with a lap of 1:26.954 for Sauber.
Qualifying is Saturday for Sunday's 66-lap race.