Spray a nine-inch baking pan or casserole dish with cooking spray. 

In a mixing bowl, combine eggs with milk and stir well. 

Place a third of the shredded cheese in the bottom of the baking pan and cover with half the bread cubes. Sprinkle with another third of the cheese and season with salt and pepper. Add half the chopped scallions and repeat layers: bread, cheese, seasonings, and scallions. 

Pour egg-milk mixture over all and cover tightly with foil. Refrigerate overnight, or for six hours.

Preheat oven to 350 degrees Fahrenheit (180 degrees Celsius). Uncover pan and bake for half an hour or until golden brown and puffed.