There are few assessments that gather valid, highly detailed data on short-term (i.e., weekly) symptom frequency/severity retrospectively. In particular, methodologies that provide valid data for research investigating symptom changes are typically prospective, expensive, and burdensome. The purpose of this study was to evaluate a new interactive and graphical assessment tool for gathering detailed information about eating-related symptom frequency/severity retrospectively over a 3-month period. A mixed eating disorder sample (N = 113) recruited from the community provided symptom data once weekly for 12 weeks and completed the Interactive, Graphical Assessment Tool (IGAT) assessing eating disorder symptoms on three occasions to determine the test–retest and concurrent validity of the IGAT. The IGAT performed marginally better than other measures for retrospective symptom frequency assessment in the eating disorders and did so at a greater level of detail than other available tools. Future research should evaluate the IGAT with other behaviors of interest.