Objective To describe and quantify independent prescribing of oncology pharmacists working in adult, ambulatory cancer centers in Alberta, Canada. Methods A retrospective chart review of oncology pharmacists prescribing in the electronic health record, ARIA® was conducted. Prescriptions from January 1, 2018 to June 30, 2018 were analyzed. Descriptive statistics were used to quantify prescription volume and class of medications prescribed. A cross-sectional analysis was then performed on a random sample to determine the type of prescription intervention and evaluate pharmacist documentation. Results Over 6 months, 3474 prescriptions were ordered by 33 clinically deployed pharmacists. The median number of medications prescribed was 7 per month (interquartile range: 1.50–27.00; Range: 0.17–79.5). When prescribing was standardized by pharmacist's time clinically deployed, the median was 21.67 (interquartile range: 5.00–79.67; range: 0.67–216.67) prescriptions per month per full-time equivalent. The most prescribed class of medication was antiemetic (24.1%). From a sample of 346 prescriptions, 172 (50%) were new medications initiated, 160 (46%) were the continuation of existing prescriptions and 14 (4%) were prescription dosage adjustments. Adherence to the specified documentation standards was 47%. Conclusions Oncology pharmacists utilize their independent prescribing to initiate and continue supportive care medications for cancer patients. The prescribing volume varied greatly among pharmacists. Opportunities exist to further engage pharmacist prescribing.