Word Count: 177/275ABSTRACT Background: EHRs allow teams of clinicians to simultaneously care for patients but an unintended consequence could result in duplicate ordering of tests and medications. We implemented a simple reminder for busy teams of clinicians in our emergency department by placing a red highlight around the checkbox of a computer-based order if previously ordered.Methodology: We performed an interrupted time series to analyze all patient visits 1 year before and 1 year after the intervention. Significance testing was performed using a negative binomial regression with Newey-West standard errors, correcting for patient level variables and environmental variables that might be associated with duplicate orders. The primary outcome measure was the number of unintentional duplicate orders.Results: After the intervention, the number of duplicate orders for laboratory orders decreased with an incidence rate ratio 0.63 (0.53-0.74) and for radiology orders decreased with an incidence rate ratio of 0.61 (0.45-0.83).Conclusion: Passive visual queues provide that provide just-in-time decision support are effective, not disruptive of workflow, and my decrease alert fatigue in busy clinical environments.