The menus haven't been there for a while, but when my wife and I rode The Canadian eastbound in 2014, each meal included a meat dish, a fish dish, and a vegetarian dish. Some meals included a fourth option (usually a second meat dish). Lunch and dinner offerings came around only once during the trip. Breakfast offerings were the same 3 of the 4 days - on the second morning, breakfast was lighter with a brunch in place of lunch at midday. Trust me and anyone who tells you the meal service on The Canadian is the best in North America for a regular service train.
We were about 4.5 hours late into Toronto and the dining crew fed us an extra meal - that was the only time entrees made a second appearance and at that meal, the kitchen crew put together different presentations for the food.