In a large mixing bowl, combine the ground bison, green pepper, green onion, mushrooms and saltine crackers. Stir in the eggs and the ground buffalo with the onion soup mix; mix thoroughly.
Press mixture into a 9 x 13 inch baking dish.
In a small mixing bowl, whisk together the ketchup, yellow mustard and brown sugar. Mix thoroughly and pour over the meat mixture, spreading evenly.