Goals from Mario Gotze and Thomas Muller secured victory for the leaders, who became the first side to win 15 of their opening 17 games in the Bundesliga.
Friday's victory moved Bayern on to 47 points, another record at the halfway stage of the season, and 10 clear of second-placed Bayer Leverkusen.
Guardiola was pleased with the way his side coped against Monchengladbach, who sit third.
"I am pleased for the team," he said. "I believe we took a big step forward towards defending our title.
"We played well against an incredible opponent. It is not easy to win here. We controlled the game.
"On Wednesday (at Stuttgart) we have a great opportunity to extend our lead with another three points."
One player not involved in Bayern's win was forward Mario Mandzukic, and sporting director Matthias Sammer revealed the Croatia international had been left out by Guardiola after poor displays in training.
Sammer denied rumours that the 27-year-old could leave the club before the end of the month, insisting he remains a vital part of Bayern's plans.
"Mario has not trained hard enough," Sammer told Sky Sport Deutschland. "The coach decided not to put him in the squad.
"He is precious to us, because he works like an animal. But he has not been doing it this time, so his absence is the consequence.
"It has nothing to do with (the future arrival of Robert) Lewandowski. He (Mandzukic) is absolutely not leaving in January."
‘The pure simplicity of the way Slot has managed the squad is probably the biggest thing I could say about him. It’s not broken, so let’s get on with it’: Liverpool legend full of admiration for Jurgen Klopp's successor at Anfield
‘I trained at Spurs and thought they’d give me a chance. But I received a letter thanking me but saying they didn’t think I was good enough – I was gutted’: How Tottenham missed out on signing Wales legend John Toshack
