Sauté beef, chicken, peppers, and onion in a large skillet in heated oil. Near the end of cooking time when meat is almost done, add the shrimp and tomatoes and cook until the shrimp is cooked through.
Serve cooked meat and vegetables with tortillas, guacamole, sour cream, and salsa. Each person assembles their own fajitas by putting meat/vegetable mixture in tortillas and topping with their choice of condiments, rolling up the tortilla, and eating by hand.
Feel free to switch this up and serve any combination of meat that you prefer.Whether or not to devein shrimp is a personal preference and is not necessary for food safety reasons. Most frozen shrimp is already deveined. If you prefer, you can cook the meat and vegetables on the grill to avoid heating up the kitchen. I like to toss the meat and vegetables with the oil before cooking, and cook them in a preheated grill on a clean vegetable grate prepared with non-stick spray.