Senior participation in the Supplemental Nutrition Assistance Program (SNAP) has traditionally been lower than other groups, with historical estimates below 50 percent. We examine the relationship between state SNAP policy changes occurring over the 2001-2014 period and SNAP participation as well the relationship between SNAP participation and a variety of health-related outcomes for senior and non-senior households. Data from three separate sources, the 2001-2014 December Current Population Survey Food Security Supplement (CPS-FSS), the 2002-2014 Health and Retirement Study (HRS), and the 2001-2014 National Health Interview Survey (NHIS), are used to conduct our analyses. We construct simulated eligibility variables (SEVs) and SNAP policy indices to capture differences in state SNAP generosity. In both our CPS-FSS and our HRS samples, we find that eligibility expansions lead to increases in non-senior SNAP participation with some evidence of smaller increases in senior participation. Overall, seniors and non-seniors appear to respond differently to various policies, but this difference is not consequential enough to explain the large participation disparity between the two groups. We also find that SNAP participation is associated with worse health-related outcomes for all samples in all three datasets, which is likely due to negative selection into program participation. The signs of these relationships reverse when we use our SEVs as instruments for SNAP participation. However, these coefficient estimates are not statistically significant and the strength of the SEV as an instrument for senior SNAP participation depends on the dataset and sample used, as well as whether or not we use sampling weights.