Set your air fryer to 350 degrees F (175°C) and let it preheat for a few minutes.
In a mixing bowl, whisk together eggs, milk, Parmesan cheese, garlic powder, oregano, salt, and pepper until fully combined.
Stir in cherry tomatoes, spinach, onion, and bell peppers.
Spray a small, air fryer-safe pan or dish with non-stick cooking spray.
Pour the egg mixture into the prepared pan. Place the pan in the air fryer basket and set cook time for 15-18 minutes.
Sprinkle mozzarella cheese on top during the last 2 minutes of cooking.
Insert a toothpick into the center of the frittata. If it comes out clean, it’s done!
Let the frittata cool for 2-3 minutes before slicing. Serve warm and enjoy!