Follow these simple, step-by-step instructions to bake a batch of perfectly cheesy and flavorful vegetable egg muffins. This recipe is designed to be easy and efficient, even for beginner cooks.

1. Preheat Your Oven and Prepare Muffin Tin: Start by preheating your oven to 375°F (190°C). While the oven is heating, lightly grease a 12-cup muffin tin with cooking spray or line it with paper or silicone muffin liners. Liners make cleanup much easier and prevent the muffins from sticking.
2. Sauté the Vegetables (Optional but Recommended): While this step is optional, sautéing your vegetables beforehand significantly improves their texture and flavor in the muffins. Heat 1 tablespoon of olive oil in a skillet over medium heat. Add your finely chopped vegetables (onions first if using, then bell peppers, broccoli, zucchini, carrots, spinach last if using). Sauté for 5-7 minutes, or until the vegetables are slightly softened and fragrant. Don’t overcook them, as they will continue to cook in the oven. Season the vegetables with a pinch of salt and pepper while sautéing.
3. Whisk the Eggs and Milk: In a large bowl, crack 12 large eggs. Add 1/4 cup of milk to the bowl. Whisk the eggs and milk together thoroughly until they are well combined and slightly frothy. Whisking incorporates air, which helps create a lighter texture in the muffins.
4. Add Cheese and Seasonings to Egg Mixture: To the whisked egg and milk mixture, add 1 cup of shredded cheese and your chosen seasonings (salt, pepper, garlic powder, onion powder, dried herbs if using). Stir everything together gently until the cheese and seasonings are evenly distributed throughout the egg mixture.
5. Incorporate the Sautéed Vegetables: Once the vegetables are sautéed (or if using raw vegetables), add them to the egg mixture. Fold the vegetables into the egg mixture using a spatula or spoon until they are evenly dispersed. Be careful not to overmix at this stage, just gently combine everything.
6. Fill the Muffin Tin: Spoon the egg and vegetable mixture evenly into the prepared muffin tin, filling each cup about three-quarters full. This allows space for the muffins to rise slightly during baking without overflowing.
7. Bake the Muffins: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the muffins are set and lightly golden brown on top. To check for doneness, insert a toothpick into the center of a muffin; it should come out clean when the muffins are fully cooked. The tops should spring back lightly when touched.
8. Cool Slightly and Serve: Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for a few minutes before gently removing them to a wire rack to cool further. Cooling slightly makes them easier to handle and prevents them from breaking apart. Serve warm or at room temperature.