Pure stands of alfalfa, bromegrass, orchardgrass and timothy, each represented by two varieties differing in maturity and/or plant type, were harvested weekly during their first crop growth in 1961, 1962, and 1963.All forages consistently increased in dry matter yield until approximately the early-seed stage. Differences in rate of growth, development and dry matter yield occurred between and within forages and years. Bromegrass, the earliest to start growth, and timothy had similar final yields of dry matter, alfalfa was intermediate and orchardgrass was lowest.At the heading stage in the grasses and at the very-first-flower stage in alfalfa, all species had stored 70% of their dry matter but 82% of their in vitro-digestible dry matter (IVD) yield. Unlike dry matter, IVD yields increased slowly after early June.The crude protein content and yield were considerably lower in the grasses than in alfalfa. Varietal yield differences within a species were small except for orchardgrass. At the suggested harvest time, alfalfa had stored 87% of its maximum crude protein yield, and the grasses, 96%.