Preheat your oven to 350°F and generously spray a 12-cup muffin tin with cooking spray.
Chop your veggies and quickly sauté them in olive oil until tender-crisp. Let them cool slightly.
Distribute the cooled vegetables and cheeses evenly among the muffin cups.
Whisk together eggs, milk, and seasonings in a large bowl until well combined.
Pour the egg mixture evenly over the vegetables.
Bake for 22-25 minutes until the eggs are set.