Spray a 9x13in backing dish with cooking spray, set aside.
In a medium bowl stir together ham, green onions, and 2 cups of the cheese.
Spoon the ham mixture onto a flour tortilla. Roll up tortillas and place in baking dish. Line them up close together so the sides touch. Repeat until the baking dish is full.
Whisk together milk, eggs, salt, and flour. Pour over tortillas.
Cover with foil and refrigerate overnight.
In the morning, preheat the oven to 350 degrees.
Bake covered for 30-40 minutes.
Remove foil and sprinkle with remaining 1/2 cup of cheese.
Bake 10 more minutes or until tops are golden brown, cheese is melted, and egg mixture is set.
Serve with salsa, sour cream, or additional green onions.