Stefan Johansen broke the deadlock with a header one minute before the break, before second-half goals from Leigh Griffiths and strike-partner Anthony Stokes sealed a comfortable win for the champions-elect.
And Lennon, whose men will secure the Scottish Premiership title if they beat Partick Thistle on Wednesday - if second-placed Aberdeen drop points at Ross County 24 hours earlier - reckoned the score could have been "anything".
He said: "I am delighted with the performance, particularly, in the second-half, when I felt we were very good.
"A wee bit wasteful in front of goals at times but I can't ask any more.
"It was another comprehensive win and another clean sheet. We are playing good attacking football and we are looking forward to every game."
Johansen, whose goal was his first for Celtic, is looking forward to his second title win in six months, having helped Stromsgodset to glory in Norway before moving to Parkhead.
"It would be two titles in about six months so it's going to be special for me," he said.
"Football is about winning. That's one thing you learn when you come to Celtic because winning is in the DNA and it's fantastic to be here. I want to win as many trophies as I can. I am enjoying my time here."
St Mirren remain in the relegation play-off spot but only three points behind eighth-placed Kilmarnock, who have played a game more.
Manager Danny Lennon vowed to put aside speculation about his future and a possible takeover of the Paisley club - reportedly by a group headed by former Cowdenbeath chairman Jim Lethven - to concentrate on keeping the team in the division.
"The football club has been up for sale since I came in and there has been a lot of parties brought to the table," Lennon said.
"Someone I know very well has introduced a group to the table but I am not party to boardroom talks, that is above my pay level. I am here to take care of football matters and not business matters, that's the way it will remain.
"My own contract situation is the furthest thing from my mind. I am totally focused in making sure we stay a Scottish Premiership club and that is where my full attention is."