Do you mean just on a piece of foil that's open? If so, yes it will dry out on you. Seal the foil up very tight when reheating in the oven. Also you can Microwave 50% power covered and stir every min till hot. Crock pot, don't over do it here, as in leave it on low for hrs on end, can dry out on you very fast. For all the above you can add some kind of liquid to it to help. Alot use apple juice, I prefer a finishing sauce or vegtable/chciken stock. IMO, vac sealing then reheating in hot water is the best way to avoid dry meat. HTH