Preheat the oven to 350 degrees F.

Spray a muffin tin with coconut oil spray.

Whisk the egg whites together with the salt and pepper in a large bowl.

Stir in the bell peppers and spinach.

Carefully spoon the egg and vegetable mixture into the muffin cups, dividing the mixture equally between the twelve cups.

Bake for 25-30 minutes or until the egg whites are set.

Remove from the oven and let cool for 5 minutes before serving.

Serve warm and topped with green onions. Alternatively, store in the refrigerator.