This article presents several of the challenges facing postsecondary mathematics education and describes how the undergraduate Learning Assistant (LA) program has been used as a catalyst to engage faculty and students in redesigning opportunities to learn mathematics. Characteristics of the LA program that have been used to transform introductory undergraduate science courses are discussed. We then describe how the LA program was implemented in a mathematics department vis-à-vis the specific contextual features of a mathematics department at the University of Colorado Boulder.