Breakfast casserole reheats very well, whether you wish to reheat it using the microwave or the oven. Microwave in 30 second intervals so you don't overdo it and dry out the eggs; or, reheat gently in the oven wrapped in foil. You can even reheat it on the stove over a gentle heat, if you prefer. I like to place a lid over the pan to keep it from drying out and to heat it through more quickly.