This article considers interaction among participation in the Food Stamp Program (FSP), food security status, and the composition of food expenditures. A quadratic almost ideal demand system with a bootstrapping two-step method of estimation is applied to data from the Current Population Survey–Food Security Supplement data and used to estimate the model and account for endogeneity between the FSP participation and food insecurity. The results show that FSP participation is endogenously related with food security status and significantly affects total food expenditure and food-away-from-home expenditures.