An informal needs assessment and lack of a national standardized curriculum has suggested that there is tremendous variability in radiation oncology resident didactics throughout the United States. The goal of this study was to evaluate the current educational landscape for radiation oncology resident didactics throughout the United States, in order to identify knowledge gaps and areas for improvement. All 91 radiation oncology program directors in the U.S. were sent an IRB approved, anonymous, 14 question survey by email in May of 2019, regarding the current implementation of resident didactics. Prior to dissemination, this survey underwent content validation by seven medical education experts, and was piloted with nine radiation oncology physician volunteer participants with subsequent cognitive interviews. 24/91 (26%) of program directors responded. The average number of residents per program was 10, faculty was 16, and hours per week spent on didactics was 6. The most common teachers during resident didactics were residents and faculty, and no fellows participated in teaching in any program. The average time a faculty member was present during didactics was 79%, with some programs having a faculty member present only 20% of the time. All but one program director (96%) stated that resident didactic time is protected from clinical responsibilities; however, 8/24 (33%) stated that residents are sometimes or often interrupted during didactic time by clinical responsibilities. Programs use a variety of teaching styles; all programs reported using lecture-based teaching, with a majority also using quizzing (67%), and only a minority using simulation (38%) and flipped classroom (17%) techniques. Other than PowerPoint, the most common electronic resource utilized was quizzing/polling (used in 16 programs), webinar (used in 8 programs), and econtour.org (used in 3 programs). There was wide variability in didactic topics, with no two programs providing an identical curriculum. Free response areas for improvement included: desire for increased faculty involvement, sharing of resources nationally across programs, and inclusion of novel topics such as: ethics, finance, practice participation, quality, contouring, simulations, grant writing, interviewing, and research/educational scholarship. The lack of a national, standardized, radiation oncology residency didactic curriculum leads to variability in its implementation and opportunities for improvement such as resource sharing, content updating, incorporation of novel evidence-based-teaching techniques, encouragement of faculty participation, and protected time for residents.