Is it best to freeze meat pies before or after baking?
After checking with two Bloggers I trust, you can freeze first or freeze after cooking. It depends on your needs, if you want it to be ready super fast when you want it, cook first and then freeze, reheating will be quicker than cooking from frozen. If it doesn't matter, then go with whatever seems like a better option to you.

Here were my sources:

http://www.simplebites.net/how-to-makeclassic-tourtiere-qubec-pork-pie/
http://hilahcooking.com/tourtiere/