Background: Public health personnel from the 28th Combat Support Hospital in Baghdad, Iraq, conducted an outbreak investigation in response to many local cases of gastrointestinal (GI) illness presenting to U.S. medical facilities. The investigation was conducted to identify the source of the illness, assess the extent of cases, and make recommendations to prevent similar outbreaks. Methods and Materials: For this retrospective cohort study, medical records and patient outbreak questionnaires were reviewed. A patient case, relative to the outbreak, was defined as any person who had developed a GI illness and presented for medical evaluation to either sick call or an emergency service at a diplomatic or military medical facility in Baghdad from 30 September to 12 October 2016. Results: A total of 123 people met the case definition. The most common presenting symptom was diarrhea (91% to 96% of cases). Other symptoms included abdominal cramps, fatigue, and headache. Most cases were military personnel (n =100). Salad was significantly associated with GI illness (70% of respondents). Five salad ingredients had significantly elevated levels of Escherichia coli. Conclusion: Mitigation strategies to reduce the probability of similar outbreaks include purchasing food solely from approved vendors or thoroughly cooking all foods, including fruits and vegetables.