Madrid remain two points behind Barcelona as Thomas Vermaelen was the unlikely hero for the European champions as they overcame stiff resistence from Malaga to win 1-0 at the Camp Nou yesterday.
Benitez's men had been held to an embarrassing 0-0 draw by newly promoted Sporting Gijon last weekend, but there was to be no repeat as Bale headed home James Rodriguez's cross inside two minutes.
Rodriguez then fired an audacious free-kick from a narrow angle into the far corner of the net to double the advantage seven minutes before the break.
Betis had a great opportunity to at least mark their visit to the Bernabeu with a consolation when Raphael Varane was penalised for upending Jorge Molina.
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However, Keylor Navas made the most of his opportunity despite the ongoing speculation that Manchester United goalkeeper David de Gea could join Madrid in the coming days by diving low to his left to save Ruben Castro's penalty.
And Bale had the final word with a fierce left-footed effort that clipped the post on its way into the net.
The Belgian defender endured a nightmare debut campaign with the Catalans last season despite being part of a treble winning squad as he was perennially sidelined by injury.
"It is a great reward for him for the fight he had last year," said Barca defender Javier Mascherano.
"I am happy for him because last year he couldn't show his best football.
"The goals from the front three will come The team generated a lot of chances, but we didn't have much luck.