French toast casserole is easy to freeze. Assemble the casserole completely, but do not bake it. Wrap tightly in plastic wrap and foil, or a freezer-safe plastic bag with the air pushed out. Label with the freezing date and freeze for up to 3 months. I recommend storing it in the same container you plan to bake it in to make it even easier. When ready to enjoy, bake it straight from the freezer at 425°F until golden brown and a toothpick inserted in the center comes out clean, about 30-40 minutes.