Zinedine Zidane's team further stretched their record-breaking winning run after the Colombia international opened the scoring, while Benzema put the result beyond doubt
Real Madrid maintained their 100 per cent record this season despite Cristiano Ronaldo and Gareth Bale sitting out the 2-0 La Liga win at Espanyol.
Coach Zinedine Zidane ruled Ronaldo and Bale out of the trip to the Estadi Cornella-El Prat due to illness and a hip injury respectively, while he handed a first start of the season to James Rodriguez.
That call was rewarded in first-half stoppage time as the Colombia playmaker fashioned space to open the scoring with an unerring 25-yard strike.
James' goal brought an end to an otherwise forgettable opening 45 minutes but Madrid operated with an easy control after the break and, having gone close on a few occasions, Karim Benzema – the remaining member of Zidane's feted "BBC" forward line – opened his account for the season to seal the victory.
Madrid sit three points clear of rivals Barcelona and surprise package Las Palmas after four matches, while Espanyol – who were left to rue a pair of first-half missed from Leo Baptistao – are still looking for their first win under Quique Sanchez Flores after two draws and as many defeats.
Madrid captain Sergio Ramos provided much of the early entertainment as he collected a deserved third-minute booking for clattering through Baptistao before powering a header wide from James' corner.
Baptistao might have still been feeling the effects of Ramos' boisterous introduction as he allowed Kiko Casilla to save in the Madrid goal following a dreadful clearance from Pepe.
Zidane suffered an unwelcome addition to his fitness concerns when holding midfielder Casemiro departed with an apparent calf injury in the 19th minute, with Toni Kroos on in his place.