Preheat oven to 350°.
Combine the milk, 1/2 cup cheddar cheese, green onions, and next 5 ingredients (green onions through eggs), stirring with a whisk.
Divide sausage and bread evenly between 2 (8 x 4-inch) loaf pans coated with cooking spray. Pour egg mixture evenly between pans. Top each pan with 1/4 cup cheese.
Cover each pan with foil. Bake at 350° for 20 minutes. Uncover and bake an additional 40 minutes or until a wooden pick inserted in center comes out clean.
To freeze unbaked casserole: Prepare through Step 3. Cover with plastic wrap, pressing to remove as much air as possible. Wrap with heavy-duty foil. Store in freezer for up to 2 months.
To prepare frozen unbaked casserole: Thaw completely in refrigerator (about 24 hours). Preheat oven to 350º. Remove foil; reserve foil. Remove plastic wrap; discard wrap. Cover casserole with reserved foil; bake at 350º for 40 minutes. Uncover and bake an additional 50 minutes or until bubbly.