01 - Preheat the oven to 350°F. Grease a 12-cup muffin tin generously or line with silicone muffin liners.
02 - In a large mixing bowl, whisk together the eggs and milk until smooth and well combined.
03 - Fold in the chopped spinach, green onions (if using), crumbled feta, shredded mozzarella or cheddar, salt, pepper, garlic powder, and nutmeg. Stir until evenly distributed.
04 - Ladle or pour the mixture evenly into the prepared muffin tin cups, filling each about ⅔ full to allow room for rising.
05 - Bake for 18 to 20 minutes, or until the egg bites are set in the center and lightly golden on top.
06 - Let cool in the tin for 5 minutes. Run a knife around the edges of each bite and gently remove. Serve warm or at room temperature.