Heat olive oil in a medium skillet over medium-high heat. Add onions, mushrooms, and red pepper and cook until vegetables are softened, about 5 minutes.
Spray a 12-cup muffin tin with non-stick cooking spray.
Divide the vegetables among the muffin cups.
In a medium bowl, whisk together eggs, milk, salt, pepper, and oregano.
Divide the egg mixture among the muffin cups and top with cheese.
Bake for 25 minutes, or until golden brown and set.
Let cool for 5 minutes before serving.
Interesting Facts
Quiches are a traditional French dish that can be served hot or cold.
Quiches can be made with a variety of ingredients such as cheese, vegetables, and meats.
Mini quiches are a great option for parties and gatherings.
Quiches can be stored in the refrigerator for up to 5 days.