Background: Increasing patient volume and treatment complexity in the field of radiation oncology has resulted in increased number of errors possibly affecting patient safety. Effective methods of mitigating these errors include automation, computerization, simplification, and standardization. To improve quality of care and patient safety, our institution established consensus standardized treatment guidelines for each cancer site. However, physician orders for computed tomography (CT) simulation for radiation treatment planning continued to have extreme variability, with error rates of 31%. Therefore, a team was assembled to devise standardized orders to reduce error, improve patient safety, and improve quality of care in the CT simulation order process. Methods: For this study, we investigated 3 commonly treated sites at our institution: breast (14%), prostate (7%), and brain metastases treated with radiosurgery (14%). A standardized template CT simulation order was defined for each disease site using the consensus treatment guidelines. These orders were integrated into the electronic medical record (EMR) on March 5, 2018. To evaluate the efficacy of the intervention, CT simulation order data were queried for the two-month period before and after implementation of standardized template orders. Orders with variation from the treatment guidelines were counted to calculate error rates with and without standardized simulation orders. Results: In the two-months prior to implementation of the standardized order templates, 48 of 151 (31%) CT simulation orders for the three selected sites had variation from the consensus standardized orders. After implementation of the EMR standardized template, 17 of 129 simulation orders (13%) in the three selected sites had variations from the standard during this two-month period. Standardization of CT simulation orders using an EMR template reduced error rates from 31% to 13% (18% absolute reduction; 42% relative reduction). Conclusions: Simplification and standardization of CT simulation orders decreased error rates by 42%, thereby improving clinic efficiency and appropriate patient treatment.