Los Blancos have now been victorious in each of their last four league matches - closing the gap on second-placed Atletico Madrid to just four points in the process.
Ronaldo netted twice for the Spanish champions, but passed up the chance to score his hat-trick in the latter stages from the penalty spot as the Portuguese allowed under-fire Benzema to get his name on the scoresheet.
As for Alaves, head coach Abelardo shuffled his pack following their 1-0 win over Deportivo La Coruna last time out.
Alexis returned to the back four, while Hernan Perez featured in the middle of the park. John Guidetti kept his spot in the final third, but he had a new partner as Ruben Sobrino came in for Munir El Haddadi.
Real Madrid were the team on the front foot in the early stages, although aside from a deflected Ronaldo effort - which missed the Alaves post - the home side were finding it difficult to create openings.
Ronaldo then struck one into the arms of Fernando Pacheco in the 17th minute, before Benzema fired wide of the post moments later having been fed by Bale on the break.
Benzema missed another sitter moments later when he hit the post from close range, but the offside flag just about spared the Frenchman's blushes.
Guidetti worked some space just outside the Real Madrid box in the 32nd minute, but the forward could only find the gloves of Navas as the score stayed goalless at the Bernabeu.
Lucas Vazquez was next to try his luck for the home side after working space in a dangerous position, but the Spaniard fired straight at Pacheco. Alaves continued to impress in the latter stages of the first period though, and Navas had to be alert to keep out a strike from Alfonso.
It was Real Madrid that made the breakthrough in the 44th minute, however, with Ronaldo spinning inside the Alaves box before firing an unstoppable low effort into the bottom corner following smart work from Benzema.
Los Blancos then doubled their lead less than one minute into the second period when Benzema raced clear before feeding Bale, who carefully slotted the ball past Pacheco to double the home side's advantage.
Benzema thought that he had made it 3-0 in the 51st minute when he swept home from close range, but the offside flag was again raised.
Benzema had missed some excellent chances, but the Frenchman continued to combine with Ronaldo and Bale in the final third as Alaves struggled to hold off the pressure.
Real Madrid's third was coming though, and it arrived just past the hour when Ronaldo swept a low Lucas cross into the bottom corner for his 28th goal of the season.
Theo Hernandez brought a smart save from Pacheco in the 66th minute as the pressure continued, before Lucas smashed the ball into the side-netting five minutes later.
As it transpired, Madrid's fourth of the afternoon came from the penalty spot in the 89th minute when Benzema found the bottom corner with a cool finish after Bale had been brought to the ground.
Real Madrid's chances of retaining the Spanish title have all but ended due to Barcelona's incredible season, although Zidane's side now have second-placed Atletico firmly in their sights.
REAL MADRID (4-4-2): Navas; Carvajal, Varane, Nacho, Theo; Lucas, Casemiro (Llorente 80'), Kovacic (Ceballos 73'), Bale; Ronaldo, Benzema
ALAVES (4-4-2): Pacheco; Alexis, Laguardia, Ely, Duarte; Perez, Garcia (Medran 63'), Torres, Alfonso (Ibai Gomez 62'); Sobrino, Guidetti (Burgui 74')