I am a Canadian, and have been working in the USA on an OPT Visa. It expires at Christmas, and I want to leave the country (to Canada) and return right away as a tourist. I heard that I can return the same day, but haven't been able to confirm this anywhere online. Does anyone know?
When exactly does your OPT expire - at Christmas as you've stated, or 60 days beforehand?
Presuming it expires at Christmas, then you are legally able to stay in the US for 60 days after expiry. You are NOT allowed to work during that period, but you can legally stay in the country for other purposes, so if you're planning to be a tourist for less than 60 days, AND you do not plan to leave the US during that time, then you're good!
Once you leave the US after the expiry of your OPT, then you are NOT allowed to re-enter using the OPT - even if it is still within the 60 day grace period.
However, as a Canadian Citizen you are allowed to re-enter the US as a tourist. Technically there is no reason that you could not do the immediately ("same day"), however as with all entries it is at the discretion of the immigration officials to determine if they believe you are entering for the purposes you're stating or not. If they believe that you are re-entering the US for the purposes of working, then they can deny your entry. How likely this is to occur will depend on your exact situation - if it were me I would have as much paperwork as possible available to show that you are a tourist rather than returning to work.