Developments during the 1960s in understanding of voluntary feed intake and energy metabolism in ruminants are incorporated into the traditional linear programming formulation of least-cost balanced rations for growing beef steers and heifers. Balancing a diet requires that the amount to be consumed (ration) be specified. However, the quantity of feed voluntarily consumed by cattle is itself dependent on diet composition. Introduction of the net energy system of designating requirements of cattle and composition of feeds demands dual specifications of net energy for maintenance and for production. Unfortunately, under the new system net energy contents of feed are no longer constant values but themselves vary according to diet composition. These considerations are included within the framework of the standard linear programming diet problem, by using an approach consisting of solving two independent but closely linked problems.