Students with disabilities are increasingly receiving their instruction in inclusive classrooms. General education teachers continue to report a lack of preparation to address their needs. This study examined the impact of a 6-hour professional development seminar on the Universal Design for Learning (UDL) framework to determine if preservice general and special education teachers’ overall performance in lesson design to reduce barriers, identified through increased attention to student variability, improved. Two lesson plans, preseminar and postseminar, from 242 participants were scored using a modified education field experience (EFE) rubric that included 19 evaluation criteria. A Rasch analysis was used to determine pretest and posttest scoring validity and to enable regression analysis with a continuous outcome variable. Results indicated that the seminar resulted in higher scores for the participants’ postmeasures, controlling for the premeasure effects, as well as unique findings based on subject matter. These findings are presented, as well as implications for future research and practice.