To store: Place baked oatmeal in an airtight container in the refrigerator. Enjoy within 3-4 days for the best flavor. Reheat in the microwave or the oven until warmed through.To freeze: Allow the tray to cool completely and store in airtight container in the freezer for up to 3 months. To reheat from frozen, place in the oven at 350°F until warmed through.Make ahead: You can make this recipe ahead of time! Place oatmeal mixture in the baking dish, cover and refrigerate. The next day, uncover and bake as directed.