Preheat oven to 350F degrees.
In a large bowl, whisk the eggs, egg whites, milk, salt, pepper, and shredded cheese together until thoroughly combined. Set aside.
Heat a 10 inch oven-safe skillet over medium-high heat (A skillet larger in size will yield a thinner quiche). Spray the skillet with nonstick spray or lightly grease with olive oil or butter.
Add sausage, onion, and garlic. Stirring frequently, cook for 5 minutes or until the sausage is a little browned.
Add the green pepper and cook for 3 minutes, stirring occasionally. Stir in the prepared egg mixture, then sprinkle with grated parmesan cheese.
Bake for 45 minutes or until filling is set and no longer jiggles. Cool for 10 minutes on a wire rack before slicing and serving.
This quiche makes great leftovers. Store tightly covered in the refrigerator for up to 4 days.
Make ahead – Baked quiche freezes well, up to 2 months. Thaw overnight and bake at 350F to warm up for 20 minutes, give or take.
Additional Notes – Don’t have the appropriate oven-proof skillet? Prepare the recipe through step 3 in any frying pan or large pot. Then pour the mixture into a lightly greased 9-inch pie or cake pan. Bake as directed in step 4.