A Liga defeat to Valencia last weekend was followed up by a Copa del Rey loss at bitter rivals Atletico Madrid on Wednesday but, although Fabio Coentrao was sent off early in the second half, Real never looked at risk of losing three games in a row for the first time since 2009.
Karim Benzema provided Espanyol with an early warning as he blasted against the post after just 10 minutes, and the breakthrough followed shortly after as James Rodriguez found the net following Cristiano Ronaldo's assist.
The FIFA Ballon d'Or nominee then watched on as Gareth Bale doubled Real's lead with a fine free-kick in the 28th minute.
The hosts' position was put in doubt seven minutes into the second half as Coentrao received a red card following a forceful collision with Jose Canas.
Yet Espanyol struggled to make the most of their numerical advantage and Real ultimately added a third through substitute Nacho Fernandez, as they moved four points clear of Barcelona and Atletico Madrid - who meet on Sunday - at the top of the table.
Elsewhere on Saturday, Valencia were held to a draw and Villarreal and Malaga also shared the spoils.
The day's other game saw Eibar overcome Getafe 2-1 thanks to goals from Manu del Moral and Ander Capa.
