Step 1: Preheat the oven to 350°F (175°C).
Step 2: Lightly grease each cup of the muffin tin with cooking spray or oil.
Step 3: In a large mixing bowl, crack all the eggs and add the milk. Whisk until well combined and slightly frothy.
Step 4: Stir in the cheeses, turkey sausage, green onions, yellow onion, and red bell pepper. Season with salt and pepper to taste.
Step 5: Pour the egg mixture evenly into each muffin cup, filling them about 3/4 full.
Step 6: Bake for about 18-20 minutes, or until the omelets are set and lightly golden on top.
Step 7: Allow to cool for a few minutes, then gently loosen the edges and pop them out.
