The aim of the study was to investigate the effect of co-precipitation of red clover protein and casein in combination with sulphite. Previous studies have shown antioxidation effects of introducing sulphite in the extraction of red clover protein for potential food applications. In the present study, it was hypothesized that casein co-precipitation in combination with sulphite would improve red clover's protein recovery, quality, and protein digestibility. The amount of soluble protein in the red clover juice was increased by the presence of casein, determined by both an increase in the total protein and in the amount of the photosynthetic protein RuBisCO. Casein treatment did not affect the in vitro protein digestibility, whereas the digestibility was increased with the addition of sulphite as an effect of phenolic oxidation inhibition.