Preheat the oven to 350 degrees.
Spray the 12 cup muffin tin with non stick cooking spray.
Saute the onion, bell pepper and mushrooms with the oil in a pan over medium heat until soft.
In a separate bowl, combine the eggs, egg whites, skim milk, seasonings, squash and cheese and mix. Then add the sauteed mix to the egg mix.
Mix the ingredients well to make sure all the ingredients is evenly distributed.
Pour 1/4 to 1/2 cup of the mixture into each muffin cup.
Bake for about 22 to 24 minutes or until it's cooked through.