Technical Abstract: Can range livestock producers reduce harvested feed inputs, during heifer development, and maintain production goals? To address this, we conducted a two year study measuring milk production (kg/d) and milk constituent concentrations (g/d) for 16 primiparous beef cows each year that were born from dams receiving adequate or marginal winter supplementation and then randomly assigned to be development treatments that provided ad-libitum or 20% less feed post weaning. Milk production was measured by using a portable milking machine every other week from d 28 to126 post partum. Milk yield for the 126-d lactation period was calculated from the area under the lactation curve approximated by trapezoidal summation. The analysis of variance model included dam winter nutrition, heifer development treatment, and their interaction. Total milk yield, day of peak yield, and peak yield did not differ between dam nutrition (P = 0.57) or heifer development treatment (P = 0.09). Milk urea N, butter fat, lactose, and solids non-fat did not differ due to dam winter nutrition (P = 0.09) and milk urea N, protein, lactose and solids non-fat did not differ between heifer development (P = 0.09). Milk butter fat was greater (P = 0.04) in heifers receiving ad-libitum feeding during heifer development (212 vs. 182 ± 9.7 g/d, respectively). Heifers born from dams receiving marginal winter nutrition had greater (P = 0.03) milk protein (211 vs. 184 ± 8.3 g/d, respectively). This study suggests that a heifer’s dam and a heifer’s plane of nutrition may influence first parity milk composition but not first parity milk yield.