Does the safety net reduce food insecurity in families? In this paper we investigate how the structure of benefits for five major safety net programs – TANF, SSI, EITC, SNAP, and Medicaid – affects low food security in families and very low food security among children. We build a calculator for the years 2001-2009 to impute eligibility and benefits for these programs in each state, taking into account cross-program eligibility rules. To identify a causal effect of the safety net, we instrument for imputed eligibility and benefits using simulated eligibility and benefits for a nationally representative sample. Focusing on non-immigrant, single-parent families with incomes below 300 percent of the poverty line, the results suggest that the median annual cash and food package of roughly $3400 reduces low food security by 5.1 percentage points on a base incidence of 33 percent, a 16 percent reduction. The same package reduces the more extreme outcome of childhood very low food security by an imprecisely estimated 36 percent. Controlling for receipt of other program benefits, the SNAP food assistance program improves food security: each $1000 in annual SNAP eligibility reduces low food security by 1.8 percentage points. We are unable to reject equivalent impacts of cash and food assistance.