كتب : Hatem Maher
The title holders would have wrapped up their 31st league title had Villarreal slumped against Betis.
But it is a matter of days for Real to win their first trophy under German coach Bernd Schuster.
Schuster took over at the club in the summer after Italian tactician Fabio Capello was sacked despite guiding Real to league victory.
Real's victory took them ten points clear of second-placed Villarreal at the league summit with four matches remaining.
They will be officially crowned champions if they beat Osasuna next week.
Javier Saviola needed 13 minutes to open the scoring against Bilbao when he poked home on the rebound after Robinho's initial shot was parried by Armando into his path.
The hosts had to thank Iker Casillas for maintaining their advantage after the Spain keeper produced a series of impressive saves to deny Bilbao on several occasions.
He also saved a penalty from Fernando Llorente with a superb one-handed block.
Substitute Arjen Robben doubled Real's lead in the 74th minute after being set-up by Gonzalo Higuain's pass.
Higuain turned from provider to scorer to wrap up the victory three minutes later.