Yes, they can. Once the pumpkin bars have been made, store them in an airtight container and place in the fridge for up to 2-3 days or the freezer for up to 3 months. When ready to eat, bring them to room temperature, make the frosting, frost and serve. Frozen bars will need to thaw overnight in the fridge and then brought to room temperature. You can also freeze frosted bars for up to 3 months.