In the U.S. and most other developed countries, animal-based proteins provide a significant portion of the human diet. However, predictions for animal protein consumption indicates that consumption in Europe and North America will begin to decline by 2035 because plant-based proteins have become accepted as having an appearance, texture, and taste that is close to that of animal products. Examples of plant based proteins that are already on the market are plant-based burgers such as the Impossible Burger and the Beyond Burger, which are produced primarily from soy and pea protein, respectively. The digestible indispensable amino acid score (DIAAS) is recommended by FAO as the best method to determine protein quality in human foods. This method allows for calculation of the protein value of both individual ingredients and combined meals consisting of several proteins. Previous research in our laboratory demonstrated that values for DIAAS obtained in milk and breakfast cereals are additive in mixed meals, and the principle of additivity is believed to be applicable to all types of combined meals, but additional research to demonstrate this is needed. Therefore, the objectives of this experiment were to determine DIAAS values for animal and plant-based burgers and test the hypothesis that DIAAS calculated for a burger and a burger bun are additive in a combined meal.