Giovani Dos Santos opened the scoring in the 11th minute when he produced a clever back heel to turn in a cross-shot from Gyasi Zardes before captain Robbie Keane doubled the advantage three minutes later when receiving a pass from Dos Santos prior to curling home from just inside area for his 16th of the season.
Dallas were back in the contest when Michael Barrios scored in the 35th minute but Steven Gerrard restored the Galaxy's two-goal buffer when poking home from close range in the 57th minute.
Atiba Harris was able to again pull one back for the visiting Texan outfit but the damage had already been done by the reigning champions' three Designated Players.
Watch the highlights below, courtesy of the Galaxy's YouTube channel:
The Galaxy remain at the top of the Western Conference table with 50 points from 31 matches, which also sees them currently leading the race for the MLS Supporters Shield.