MacLennan held a comfortable lead going into Saturday's final but needed the extra cushion from Friday's preliminaries to finish first overall with a combined score of 154.665 points.
"I had a really good start in the final but on my last skill the judges ruled it was a repeat of an earlier skill so I didn't get the difficulty score," said MacLennan, who finished behind both Page and British teammate Emma Smith in Saturday's final.
Page won the silver medal with a combined score of 154.385 points and Toronto's Samantha Sendel took bronze with 151.621 points.
MacLennan, forced to delay her planned return to competition at the Canadian championships in May because of an ankle injury, said it felt "great" to get back into competition for the first time since winning gold at the London Olympics last August.
"I wasn't as confident as I would have liked going into this meet because of the lack of preparation time but overall it felt really good. My goals were to get through my routines and just get back out there in front of the judges and get used to that environment again."
In the men's competition, seven-time Canadian champion Jason Burnett of Toronto, ranked sixth after prelims, mounted a comeback to overtake Japan's Daiki Kishi for the title, but had to settle for the silver medal with a total score of 162.560 points.
Kishi finished almost three points behind Burnett in the final, but managed to cling to first place overall due to his higher scores in the prelims, edging Burnett for the gold with a score of 162.940.
France's Sebastien Martiny placed third with 161.770 points.
"I've stuck with the same routine for the last four or five months and I'm feeling quite comfortable with it," said Burnett, whose optional routine with a difficulty of 17.6 far surpassed any of the other competitors in the men's final.
"Everything is on course for the World Cups later this summer and world championships in the fall and if I need to, I'll throw in a skill or two in the finals just to boost my difficulty a little bit more."
Burnett, the silver medal winner at the 2008 Olympics, holds the world record of 18.8 for degree of difficulty.
In other events, hometown favourite Corissa Bouchuk of Airdrie, Alta., and Keegan Soehn of Red Deer, Alta., won gold in women's and men's double mini trampoline and Greg Townly and Lucie Colebeck of Great Britain won the men's and women's tumbling titles.