Ronaldo received a two-match ban after lashing out at Cordoba's Edimar in Real's last league outing, but the leaders marched without the Portugal forward at Santiago Bernabeu.
Sociedad, who beat Carlo Ancelotti’s side 4-2 at the Anoeta in September, were out to record their first away win over Real since 2004 and they enjoyed a fine start, as Aritz Elustondo headed them in front in the first minute.
James Rodriguez equalised just two minutes later, but Sociedad carried a serious attacking threat until Carlos Vela's injury 17 minutes in.
The hosts began to take control after the Mexico striker's substitution and Sergio Ramos put them ahead eight minutes before the break with his 41st Liga goal, with Benzema adding a third early in the second half.
Real saw several chances go begging in the second half, but Benzema completed the scoring in spectacular fashion with 14 minutes to go as Real moved four points clear of Barcelona, who face Villarreal on Sunday.
The visitors made a breathtaking start at the Bernabeu and broke the deadlock in the first minute, as Elustondo rose highest to meet Ruben Pardo's corner with an unstoppable header.
Moyes' men had barely finished celebrating when the hosts equalised just two minutes later, though.
Rodriguez darted in front of Yuri in anticipation of a cross and placed a fine header into the top-left corner when Marcelo's delivery eventually arrived.
Sociedad went close to retaking the lead a few moments later, as former Real midfielder Sergio Canales poked agonisingly wide after latching on to Esteban Granero's wayward effort.
But the away side's chances of securing a surprise win suffered a blow with Vela's forced withdrawal due to injury in the 17th minute and Real took control from then on.
Sociedad were forced to withstand waves of attacks and their resistance eventually broke in the 37th minute, Ramos lashing home from close range after Jeronimo Rulli denied Benzema.
It should have been 3-1 three minutes later, but Gareth Bale saw his effort deflected wide of an open goal after taking the chance off Rodriguez.
Bale made amends for that mistake six minutes into the second half, however, as the Wales forward raced down the left and cut a well-placed pass back for Benzema, who steered home a simple finish.
The visitors' attacking threat had long since diminished and Ancelotti’s side looked certain to add a fourth in the 56th minute, but the terrific Marcelo could not beat Rulli after collecting Benzema's clever pass.
Benzema rounded off a fine individual display in the 76th minute, combining well with Isco before curling a sensational strike into the top-right corner from 20 yards, doubling his tally as ruthless Real claimed a comfortable win.
‘He instantly popped into our ratings as one of the best U21 midfielders in Europe. The impressive thing is Slot has made him into more of a no.6' Inside Ryan Gravenberch's transformation at Liverpool
‘I don’t think Liverpool would look at Ollie Watkins, a striker isn’t a pressing issue for them – it’s Arsenal who need one’ Former Reds star explains why his old club don’t need an out-and-out forward this summer
