The OAC Union cultivar of soybean [Glycine max (L.) Merr.] is semi-determinate, has large seeds suitable for food-grade purposes, and offers high yield potential with elevated concentrations of seed protein and oil. Additionally, it displays resistance to soybean cyst nematode. OAC Union is developed and recommended for soybean-growing areas in southwestern Ontario with 2800 or greater crop heat units and has a relative maturity of 1.4.