A food service system comprising a cart that is movable from a central food preparation location to a remote food service location. The cart is insulated and has a rack for a plurality of individual meal service trays. Each tray carries cold foods in suitable dishes and a heat-retaining food service unit for food which may be either hot when placed therein or may be heated by connecting each unit to a source of electrical energy at the service location. The cart has conduit means which are connectable to a source of chilled air at the service location in order to keep the cold foods cold for a period of time while the food in the units is being heated to a desired serving temperature. If desired, instead of heating the food in the units at the service location, the heat-retaining units may be heated prior to departure from the food preparation location and will maintain the food therein at elevated temperature for a period of time, even while the cart is connected to the chilled air source for keeping the cold foods at a refrigerated temperature.