Luis Enrique's side dominated the match from start to finished and thoroughly deserved to win by such a comfortable scoreline.
Lionel Messi opened the scoring in the 16th minute after he played a one-two with Arda Turan, sweeping home the return ball from his fellow forward.
Monchengladbach held firm for the rest of the half, but Barca, and specifically Arda Turan, really turned the screw in the second 45 minutes.
Less than five minutes into the second half, Denis Suarez broke down the right and crossed for Turan. The cross took a deflection on the way to the Turkey international at the back post and Turan was on hand to nod the ball home from close range.
Just three minutes later, Turan had his second and Barcelona's third. Messi played in Aleix Vidal down the right who pulled the ball back for Turan, fired his perfectly placed effort into goalkeeper Sommer's bottom left corner.
Monchengladbach felt aggrieved when forward Hahn appeared to be brought down by Mascherano as the away side made a rare burst forward, but appeals for a penalty were turned down and this was as good as it got for the Bundesliga side going forward.
While Turan may have enjoyed a successful evening, fellow forward Paco Alcacer continued his poor form since joining from Valencia. The striker's best attempt saw him fire a shot straight at Sommer, but apart from that, the former Valencia man looked bereft of confidence in front of goal.
Turan managed to get his hat-trick and Barcelona's fourth in the 67th minute. Barcelona once again had joy down the right. This time, it was Alcacer who played a low cross from the right side of the box and Turan was at the back post once again to smash his third effort past the Monchengladbach 'keeper.
Barca almost had a fifth, but credit must go to Sommer who pulled off an incredible save to prevent Messi's diving header.
Enrique's men saw the game out and made it 15 points from six Champions League games, finishing six points ahead of second-placed Man City.