This study posits a theoretical framework for understanding the role and value of agency input in presidential-legislative policy making. The author asserts that by using agency input for policy development, presidents instill their proposals with a degree of bureaucratic objectivity, expertise, process transparency, and agency support, which aids their legislative passage while lowering the extent of changes made to policy substance in the process. To test his hypotheses, the author conducts binary and ordered logistic regression analyses using pooled cross-sectional data across 12 administrations from 1949 to 2010. The author finds that agency input serves as a key component for increased presidential-legislative success.