Background: Randomized controlled trials are the gold standard for assessing the efficacy of new cancer therapies and are required for marketing approval. However, participants enrolled into trials are often not representative of the more diverse populations in whom treatment will ultimately be delivered. Real-world data can be used to potentially bridge this gap by evaluating the effectiveness and safety of therapies in more generalizable populations. In this study, we describe differences in demographic and clinical characteristics between participants enrolled in a phase III trial of adjuvant chemotherapy for colon cancer and a contemporary comparator cohort using structured oncology electronic medical records (EMR) data. Methods: We drew upon publications from the Multicenter International Study of Oxaliplatin/5 Fluorouracil/Leucovorin in the Adjuvant Treatment of Colon Cancer (MOSAIC) recruiting patients primarily from Western Europe with stage II or III colon cancer from October 1998-January 2001. This trial established FOLFOX (oxaliplatin + 5-FU) as the standard of care over 5FU alone in treating stage III colon cancer and led to US marketing approval. For comparison, we identified patients diagnosed with stage II or III colon cancer (September 2014-2020) who received FOLFOX in the IQVIA US Oncology EMR database via E360, IQVIA’s Real World Discovery and Analytics platform. In the two populations, we described distributions of prognostic factors including age, sex, stage of disease, body mass index (BMI), and Eastern Cooperative Group (ECOG) performance status. Results: The MOSAIC trial included 2,246 participants; we identified 4,566 patients starting FOLFOX in the EMR comparator. Median age was similar: 61 versus 62 years, but the range differed (19-75 years versus 18-85 years) in the trial and EMR comparator, respectively. Female sex was similar at 44% and 48%, while the proportion of patients with stage III disease differed considerably at 60% and 84% for trial and EMR comparator, respectively. Half (51%) of all EMR patients were missing ECOG status; among those with a reported ECOG status, 96% had a score of 0-1, while 87% of trial participants had an ECOG of 0-1. BMI was missing in 34% of patients in the EMR comparator; among those with a reported BMI, 28% had a BMI < 25, while 54% of trial participants had a BMI < 25. Conclusions: Colon cancer patients receiving FOLFOX in an EMR comparator had a similar age and sex distribution as MOSAIC trial participants, but were more likely to have stage III disease. Missing ECOG and BMI data were common in the EMR comparator, which limited comparisons. Structured oncology EMR data represent an important resource for generating real-world evidence; future data enrichment efforts focused on critical patient-level variables via unstructured EMR extraction may improve data completeness and quality.