All the talk pre-match was about the decision to hand Thibaut Courtois his debut for the club between the sticks, but he was a spectator for long spells as 'Los Blancos' dominated the game.
Marco Asensio went close inside six minutes, dinking onto the roof of the net with only Ivan Cuellar to beat, but the hosts weren't made to wait long for the breakthrough.
With 17 minutes on the clock, Ramos picked out the marauding Dani Cavajal with a raking ball forward and the full-back nodded the ball down for Bale to fire a right-footed volley through Cuellar and into the corner first time.
September 1, 2018
At that point Madrid were in complete control, but they shot themselves in the foot seven minutes later as Casemiro tripped Javier Eraso, handing Lega an opportunity to level.
Loanee Guido Carrillo did the honours from the spot, sending Courtois the wrong way to restore parity.
The minnows largely frustrated their more reputable opponents for the rest of the half, with Benzema going close to restoring the lead when his low volley from a Marco Asensio cross was well kept out by Cuellar.
Real Madrid exploded into life after the interval with Benzema finding the net just two minutes after the restart.
The Frenchman nodded home another Asensio cross from the left and whilst the strike was initially disallowed, with Benzema adjudged to have fouled his marker, that decision was overturned by VAR and the goal was allowed to stand.
September 1, 2018
There only looked like being one winner form there on out and so it proved as Real Madrid quickly took a commanding lead.
Toni Kroos went close with a sweetly-struck volley, before Benzema doubled his tally for the day. The forward producing a lovely turn on the edge of the box, exchanging passes with a team-mate and firing home low from 18 yards.
Ramos but the icing on the cake with 67 minutes gone, stroking home a penalty after Asensio had been brought down by Unai Bustinza.
Isco could have added further gloss to the scoreline late on, but managed only to shoot straight at Cuellar after meeting a cross form the right deep into stoppage time.
The victory leaves Real Madrid comfortably top of the table, with arch-rivals Barcelona needing a win tomorrow against Huesca to keep pace. Leganes drop to 19th.
September 1, 2018