Objective: Defaults have been shown to impact decision making in a variety of domains. However, no research has applied defaults to medical care decisions utilizing an Electronic Health Record (EHR). This research was designed to examine how providers’ inpatient laboratory ordering practices were influenced by default selections in EHR order sets. Method: Providers were asked to complete inpatient admission orders for six fictitious pediatric patients using three EHR interface designs: opt-in (no laboratory tests preselected), opt-out (all laboratory tests preselected), or recommended (only laboratory tests recommended by pediatric experts preselected). EHR design was manipulated within subjects. Seventy-two providers from a Midwestern pediatric hospital reviewed the six cases and completed admission orders for all cases, entering two cases with each EHR design. Order of the cases and EHR designs were counterbalanced across participants. Results: When all laboratory tests were preselected, providers ordered significantly more tests and increased the cost of admission by more than $70 when compared with the opt-in, p < .01, and recommended EHR designs, p < .01. Furthermore, providers ordered more tests recommended by the pediatric experts when using the recommended design than when using the opt-in design, p = .03, although the total number of tests ordered did not differ significantly, p = .97. Conclusions: This study demonstrated that default selections in an EHR can significantly influence providers’ laboratory test ordering practices and that hospital systems could benefit from adding expert-recommended defaults to EHR order sets.