The Argentine sensation was at his predatory best, scoring twice in a game devoid of much goalmouth action to send the hosts further ahead at the top of the table
With Lionel Messi in deadly form once again, the Blaugrana made it 11 wins out of 12 in the new campaign with a professional and clinical performance in front of their home fans.
Messi opened the scoring 15 minutes into the game with a delightful move and finish, but Montanes pounced on a momentary defensive lapse to steer Zaragoza level 24 minutes in.
But four minutes later, Messi was at it again, this time teeing up Alex Song to score his first ever Barca goal since his summer move from Arsenal.
Messi added another brilliant effort on the hour mark to put the result beyond any doubt, and rack up his 50th goal in the 33 league games he has played in the calender year 2012, while putting the Blaugrana six points ahead of nearest challenger Atletico Madrid.
Carles Puyol returned from injury to begin the match alongside Gerard Pique in the home side's defense, which was further changed by the inclusion of Martin Montoya instead of Dani Alves at right-back.
Barca needed only two minutes to carve out its first opening, when Jordi Alba delivered a low cross to the boot of Messi after a surging run down the left, but the Argentine drilled his first time effort wide of the post.
But on the quarter-hour mark, the pair would combine again to devastating effect. From out wide, Alba played Messi infield, whose first touch took Alvaro Gonzalez out of the equation, and allowed him the time and space to slot into the corner.
Zaragoza, to its credit, did not allow its head to drop after conceding, and forced Barcelona into a bit of defending by winning a succession of corners.
And on one such set piece 24 minutes in, a slightly weak clearance from Martin Montoya was pounced on by Montanes, who drilled past Victor Valdes from the edge of the box via a slight nick off Puyol.
But four minutes later, Barcelona was back in front. Messi was the provider this time, jinking past two defenders on the left before showing great awareness to cut back to the unmarked Song to sidefoot home from 12 yards out.
Andres Iniesta nearly added a third moments later when he slipped past the defensive line on a threaded pass by Messi, but with the angle diminishing by the second, he could only hit the side netting.
With one hour gone, Barca turned up the tempo just long enough to put the game out of reach of the visitors.
Messi started the move by releasing the unmarked Montoya down the right, and the full back returned the ball to the Argentine at the top of the box, who then curled a delightful effort into the far side of the goal.
Zaragoza was utterly floored by the setback, and Barca was able to kill the game off with long spells of leisurely possession in the opposition half, forcing the already tired visitors into even more hard work off the ball.
Barca was able to close out a professional performance with a deserved victory, while Messi moves ever closer to Gerd Muller's 85 goal record.