Even though cooking steak in the oven works amazingly well, reheating leftovers later doesn’t follow the same process. Since the meat is already cooked at that point, 400 degrees can be excessively high. Instead, it’s better to slowly reheat the steak at a lower temperature such as 275 degrees over a longer period of time.
This will help the meat retain its moisture and keep the steak from getting tough or chewy. While it might be tempting to use the microwave and have your meal done faster, that will sacrifice the quality of the steak and could result in a disappointing dinner.