Mix eggs, flour, salt, nutmeg, and pepper.
Whisk in half and half and milk.
Stir in cooked vegetables, cheddar cheese and 1/2 cup Parmesan cheese.
Coat 4-quart (or larger) slow cooker with cooking spray and pour mixture into it.
Sprinkle remaining 1/2 cup Parmesan cheese on top.
Cook for 1 1/2 hours on high or until center is set.