You have to maintain a safe holding temperature and food quality when keeping a dish warm. Maintaining a safe holding temperature -- between 140 and 150 degrees Fahrenheit -- seems easy enough, but the exact temperature that ovens hold food at varies depending on how full it is and its temperature minimum, so you have to monitor the food's -- not the oven's -- temperature. To maintain quality, only hold food for 15 to 20 minutes and rehydrate it by adding water or stock to the dish when you see it drying out.
How to Keep Food Warm in the Oven
Things You'll Need
Take the dish out of the oven and lower the oven temperature to Warm or its lowest temperature, commonly between 225 and 250 degrees Fahrenheit.
Cover the dish tightly with aluminum foil. Insert an oven-safe thermometer through the foil and into the food.
Place the dish in the oven and wedge a folded towel in the oven door to keep it open about 1 to 2 inches when the oven reaches 225 to 250 F.
Check the thermometer every five minutes to ensure the food remains at least 140 degrees Fahrenheit; if it starts to dip below, close the oven door all the way.
Always reheat food to 165 F before serving.