Please help with breakfast casserole
How much longer, than overnight, do you intend to leave the casserole? What are the 'iffy' ingredients that concern you?
I have made the basic egg-milk-bread mixture and transported it (in a cooler & Ziplock bag) to be fully assembled and baked several days later when the rest of the ingredients were added.
Perhaps if you shared your recipe, we might be of more help.