In a bowl, mix together the spinach, onion, black beans, corn, and taco seasoning.
Beat together eggs and milk, then scramble them.
Split the eggs between the four tortillas, then top with the bean mixture and cheese.
Fold tortillas over and freeze in a freezer-safe bag.
To reheat: Thaw overnight or defrost in a microwave. Microwave for 2 minutes or until cheese is melted.