What sort of graduate studies are you talking about?
For any sort of research oriented Master's/PHD:
Science & Engineering: NSERC
Health Research: CIHR
Social Sciences & Humanities: SSHRC
All of which at least administer Canada Graduate Scholarships, and NSERC gives out lots of awards as well.
The applications for NSERC are due in the fall. I don't know about the others
For any graduate studies in Ontario:
OGSIn research oriented master's programs, they may also offer "soft funding" which means the university guarantees you Teaching/Research assistant jobs and the like. Depending on the university those can pay quite well.
Note that there is a difference between professional and graduate programs. Graduate program refers to a Master's or PhD program; professional is something like Medicine, Law, Teaching, etc.