Approximately one in five U.S. young adults suffer from psychiatric disorders annually. The prevalence of psychiatric disorders is even more significant in college students. Despite the large population of college students who experience mental health disorders, they are unlikely to receive treatment on their campuses, even though campus health clinics routinely offer mental health services. Furthermore, college mental health services cannot meet the growing needs of their students. In addition to other psychiatric concerns, eating disorders might be one concern slipping through the cracks. Many eating disorder treatments are intensive, expensive, and differ depending on diagnosis, which can make treatments difficult to implement on college campuses. A solution is to deliver cost-effective group-based prevention programs. One of the most rigorously tested is the "Peer Body Project," which has shown reductions in thin-ideal internalization, body dissatisfaction, and eating disorder symptoms. The "Peer Body Project" has promising evidence for meeting the needs of campuses, but moving to large-scale implementation may pose challenges for fidelity and require modifications and adaptations, especially given cultural diversity. The primary aims of the study were to explore the extent to which general and cultural modifications and adaptations impacted treatment outcomes and test if ethnicity/race moderated effects. Exploratory analyses assessed the relationships of modifications and adaptations with peer educator characteristics, group composition, and ethnic/racial matching. Modifications and adaptations occurred in every intervention group, with 50% of groups implementing cultural modifications and adaptations. Ethnicity/race did not moderate the relationship between modifications and adaptations and treatment outcomes. Exploratory analyses indicated that the more groups a peer educator facilitated, the more general and cultural modifications and adaptations they implemented. Additionally, greater diversity in group composition predicted more cultural modifications and adaptations. Finally, ethnic/racial matching between an individual and other group participants predicted more cultural modifications and adaptations. Also, an ethnic/racial matching between an individual and their group leader predicted better outcomes on thin ideal internalization. The study reveals trends on the impact of modifications and adaptations on treatment outcomes, but a larger sample, especially of minoritized individuals, may be needed to provide a better understanding of these relationships. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]