Prepare the Frittata

1. Preheat the Oven: Preheat your oven to 375°F (190°C). Grease a baking dish (such as an 8×8-inch square pan) with olive oil or butter.
2. Whisk the Eggs: In a large bowl, whisk together the eggs, milk, salt, and pepper until well combined.
3. Cook the Veggies: In a skillet, heat a bit of olive oil over medium heat. Add your diced vegetables (and cooked bacon or sausage if using) and sauté for about 5-7 minutes, or until they’re softened.
4. Combine: Stir the sautéed veggies into the egg mixture, followed by the shredded cheese.
5. Bake: Pour the mixture into the prepared baking dish and spread it out evenly. Bake for 18-20 minutes, or until the eggs are set and a toothpick comes out clean from the center.
6. Cool and Slice: Let the frittata cool for a few minutes before slicing into squares.