Legumes and grasses are widely grown in mixtures throughout the United States and Canada. This study was conducted to determine the changes in chemical composition of herbage that occur as proportion of legume and grass change in the mixture. Composition of mixtures of alfalfa (Medicago sativaL.) and orchardgrass (Dactylis glomerataL.) were studied after their herbage had been mixed by weight into seven different proportions: 100% alfalfa ‐ 0% orchardgrass, 80% ‐ 20%, 65% ‐ 35%, 50% ‐ 50%, 35% ‐ 65%, 20% ‐ 80%, and 0% ‐ 100%, respectively. The forages were grown in rows of pure alfalfa or pure orchardgrass spaced 45 cm apart on fertilized Dodge silt loam (Typic Hapludalf). Alfalfa was at late bud and orchardgrass was a few days from the appearance of the first anthers when harvested on May 29, 1975. Four replications of each of the mixtures were prepared, and the mixtures were made after tissues had been ground to 40‐mesh size.