When You Reheat Food Heat cooked, commercially vacuum-sealed, ready-to-eat foods, such as hams and roasts, to 140 °F. Foods that have been cooked ahead and cooled should be reheated to at least 165 °F. Reheat leftovers thoroughly to at least 165 °F. Reheat sauces, soups, and gravies to a boil. On Stove Top-Place food in pan and heat thoroughly. The food should reach at least 165 °F on a food thermometer when done. In Oven-Place food in oven set no lower than 325 °F. Use a food thermometer to check the internal temperature of the food. In Microwave-Stir, cover, and rotate fully cooked food for even heating. Heat food until it reaches at least 165 °F throughout. In Slow Cooker, Steam Tables or Chafing Dishes-Not Recommended Reheating leftovers in slow cookers, steam tables or chafing dishes is not recommended because foods may stay in the "danger zone," between 40 and 140 °F, too long. Bacteria multiply rapidly at these temperatures.