The Core Outcome Set for Therapeutic Studies in Eosinophilic Esophagitis (COREOS) collaborators are a group of more than 70 gastroenterologists, pathologists, allergists, researchers, dietitians, psychologists, and methodologists who convened in a series of in-person and virtual meetings between 2018 and 2020 with the aim of developing a core outcome set (COS) for use in therapeutic studies of pharmacologic and dietary therapies for the treatment of eosinophilic esophagitis (EoE). Given heterogeneity in reported outcomes and uncertainties regarding the most appropriate end points for use in both randomized controlled trials (RCTs) and observational studies involving EoE patients, the EoE experts launched the COREOS exercise in 2018 to standardize outcome definitions using methods established by the Core Outcome Measures in Effectiveness Trials (COMET) initiative.1,2 The COS was developed using a multiphase approach, which is summarized in Figure 1. In the first phase, systematic reviews of the literature and patient engagement surveys were conducted to identify candidate outcomes that have been previously measured and are important to patients with EoE. Next, this information was used to build a framework of different outcome domains, and working groups for each domain were assembled to review the literature for relevant end points.3–6 The relative importance of these domains was categorized in a Delphi survey as core, important, and research agenda domains, and discussed in a moderated in-person meeting on May 17, 2019 at Digestive Disease Week (San Diego, CA). In phase 3, a comprehensive list of outcome measures within each of the core domains was evaluated by the COREOS collaborators in a 2-round Delphi survey and, finally, outcomes were ratified in a virtual meeting on December 8, 2020. In this meeting summary, we highlight the major points of discussion that occurred during the development of the EoE COS.