A growing number of outpatient providers utilize electronic health records (EHR) to identify patient visits for influenza-like illness (ILI) but no standard query guidance exists. We applied an ILI definition validated for emergency department data to EHR from outpatient networks and found ILI visits highly correlated with influenza laboratory detections. Incorporating ambulatory EHR into our ILI surveillance system increased the capacity by more than 300%. Electronic ambulatory care data could be used to augment or replace public health surveillance systems traditionally reliant on manual reporting.