An outbreak of gastroenteritis occurred among at least 47 persons attending a school potluck. Illness was associated with consumption of ground beef (estimated odds ratio, 16.3; 95% confidence interval, 2.2 to 338.3). Salmonella Typhimurium isolated from infected individuals and the implicated ground beef revealed identical pulsed-field gel electrophoresis patterns and was multidrug resistant. The implicated ground beef was improperly handled during the cooking process and stored above the U.S. Food and Drug Administration cooling temperature standard for >15 h before being served. This outbreak demonstrates the limitations of food safety regulations in settings where foods are prepared in the home environment for communal potlucks, bake sales, or other such gatherings held at schools, churches, or other institutions. Public health authorities should encourage school and other institutional administrators to develop policies that require dissemination of safe food preparation guidelines to prospective food handlers when such events are scheduled.