Preheat over to 350 degrees. In a skillet over medium heat, saute onion and green pepper in butter until tender. In a bowl, beat eggs, then add cracker crumbs, shredded cheese, mushrooms, sauteed vegetables, meat, salt, and pepper. Mix thoroughly.
Spray small muffin tins very well with cooking spray. Fill tins to top with egg mixture. Bake in preheated oven for 25 minutes. Makes 48 to 50 tarts. Enjoy!