The effects of varying proportions of textured soy protein (mixed with ground beef) on the evap orative loss, cooking yield, lipid content, lipid oxidation, and overall acceptability were studied in cooked patties containing 0 to 40 percent soy protein. All analyses were made of patties cooked immediately after thawing. Lipid oxidation determina tions were also made after 48 and 72 hours of refrigeration. The results showed that when com pared to all beef patties the cooking yield was significantly (p<0.05) higher for those containing 30 and 40 percent soy, and the evaporative loss was lower (p<0.05) for the patties containing 40 percent soy. Total lipid content was significantly less (p<0.05) in all samples containing soy protein. Compared to 100 percent ground beef, there was less (p<0.05) fat oxidation in samples containing 30 percent soy which were refrigerated 48 and 72 hours, and in samples containing 40 percent soy refrigerated 48 hours. Overall acceptability was lower for all soy protein/beef patties as compared to those made of 100 percent beef (p<0.05).