Place the pan in the microwave oven and cook the meatloaf at medium-high temperature for five minutes. Change the heat setting to high after five minutes and continue cooking for 15 minutes. Remove the meatloaf from the microwave oven after 15 minutes, and cover it with a lid or aluminum foil. After five minutes, use a meat thermometer to check the temperature. You can safely serve meatloaf if it is at least 160 degrees F.