In the surgery-first approach (SFA), orthognathic surgery is performed without the need for presurgical orthodontic treatment. This study was aimed at assessing the treatment durations and occlusal outcomes for a consecutive cohort of patients, with a range of dentofacial deformities, who had completed orthognathic treatment using SFA. The duration of orthognathic treatment was measured. The overall change in occlusion, and the quality of the final occlusion, were evaluated using the patients’ study casts. A single, independent, calibrated operator carried out the occlusal scores, using the validated Peer Assessment Rating (PAR) index. This was repeated to test intraoperator reliability. A total of 51 patients completed surgery-first treatment during the study period. The mean (range) age at surgery was 23.3 (15–47) years. The pre-treatment skeletal jaw relationship was Class III in 39 cases, and Class II in 12 cases. The mean (SD) overall treatment duration was 11.7 (5.7) months. The intraexaminer reliability of assessing the occlusion was high. The PAR scores confirmed a significant improvement in the quality of occlusion at the completion of treatment, which compares favourably with previous studies on the conventional orthodontics-first approach. The surgery first approach can be effective at correcting both Class II and Class III malocclusion types with reduced treatment times.