Size of breeding groups and resource quality (carcass mass) were varied independently in experiments using the burying beetle, Nicrophorus defodiens, to examine reproductive output of beetles using carcasses exposed to carrion competitors. Male-female pairs experienced the same rate of brood failure as groups of four beetles (two males and two females). Groups of four produced more total larvae and a greater brood mass than pairs on large but not small carcasses, whereas reproductive output per female was lower for groups. Carcasses prepared by groups of two males and two females attracted similar numbers of free-flying congeners as carcasses prepared by pairs. The ability of more than two individuals to produce a larger brood than that of pairs may decrease the costs of communal breeding on larger carcasses, but by itself, is not sufficient to explain the evolution of breeding associations consisting of multiple females.