01 - Preheat oven to 375°F and grease a 12-cup muffin tin thoroughly with cooking spray or butter.
02 - In a large mixing bowl, whisk eggs, milk, salt, pepper, and garlic powder (if using) until mixture is well blended.
03 - Prepare add-ins by chopping all vegetables, shredding cheese, and cooking and crumbling selected meats as required.
04 - Evenly distribute vegetables, cheese, and meats into prepared muffin cups, then pour egg mixture over fillings until cups are about three-quarters full.
05 - Place tin on center rack and bake for 18 to 22 minutes, or until egg muffins are set and tops are lightly golden.
06 - Allow muffins to cool in the tin for 5 minutes, then gently release each muffin with a knife or spatula.
07 - Serve warm, or cool completely before storing in an airtight container in the refrigerator or freezer for later consumption.