1. Preheat oven to 375 degrees F (190 degrees C).
2. In a large mixing bowl, combine the ground beef, green pepper, green onion, mushrooms and saltine crackers. Stir in the eggs and the beef with onion soup mix; mix thoroughly.
3. Press mixture into a 9x13 inch baking dish.
4. In a small mixing bowl, whisk together the ketchup, yellow mustard and brown sugar. Mix thoroughly and pour over the meat mixture, spreading evenly.
5. Bake in the preheated oven for 1 hour.