Peking Dragon Restaurant is a great place for late-night food in uptown Calgary. They have a huge take-out menu and are open until 2am on Fridays and Saturdays. Last time I went we got a big container of rice noodles, sauteed veggies, and gluten-free ginger beef (made with corn starch -- yes!). The owner gave us a table and tea while we waited which really wasn't too long.
There really isn't too many places to get great quality food in the early hours of the day but Peking Dragon is a really great place to get some! Next time you are hungry in the middle of the night, head over there or order from their delivery menu!