Ronaldo opened the scoring with a twice-taken penalty in the first half and then Higuain and substitute Benzema added two more in the final 11 minutes.
Neither side finished the match with a full compliment of players, with Madrid defender Pepe the first to be sent off in the 60th minute, before Espanyol duo Ernesto Galan (63) and Juan Forlin (89) also received their marching orders.
"In light of the circumstances I'm satisfied because it is not easy to play on a potato field. Moreover there is little time to recover between games and play against an opponent that has nothing to lose," said Real coach Jose Mourinho.
"I was born in a country with 10 million coaches and I am working in a country with 40 million coaches. But the reality is only this: Madrid has only one coach and only one can decide. My team was tired, very compact and losing control. From there came the changes."