In 2010, Edyburn raised questions about the concept of Universal Design for Learning (UDL) and its implementation and wondered if it would fulfill its promise, or whether a decade later it would be viewed as just another educational fad. The purpose of this chapter is to examine two quantitative metrics to determine whether or not the term UDL is used in patterns consistent with educational fads. In addition, an overview of six UDL research synthesis studies published between 2010–2018 is provided to explore whether or not three foundational issues have been addressed: (a) operational definition of UDL, (b) identification of the active ingredients in claims of UDL interventions, and (c) measurement of the outcomes of UDL interventions. The implications of the findings are presented with consideration to the future of UDL and the design of instructional materials for inclusive education.