'Bragg’ soybeans harvested at the green-mature (GM) or dry-mature (DM) stage, 4-day sprouts (S) (both raw and heated), and cooked ‘Early Green’ GM soybeans were evaluated for protein quality, sulfur amino acids and trypsin inhibitor (TI) content. Adjusted PER values for raw GM, DM and S were 0.77, 0.75 and 0.64, and for heated diets 2.05, 2.11 and 2.02, respectively. Cooked ‘Early Green’ PER was 2.14; TI content was about l/3 as great in raw S, relative to raw GM and DM diets. There was no significant difference in total sulfur-containing amino acids among maturities nor in PER values between heated diets at the three maturities. Although soybean protein quantity increased slightly with maturation and sprouting, quality was relatively independent of maturity.