Transplants of culture-expanded bone marrow stromal cells (BMSCs) combined with hydroxyapatite/tricalcium phosphate (HA/TCP) scaffolds successfully form cortico-cancellous bone to reconstruct the dog craniofacial skeleton. Yet, these transplants' long-term stability in large animal models has not been evaluated. This study's purpose was the evaluation of long-term BMSC transplant stability when used to augment the mandible. Here, autologous BMSC-HA/TCP transplants were introduced onto the unilateral dog mandible as onlay grafts, while contralateral control mandibles received HA/TCP onlays alone. Quantitative CT (qCT) scans were obtained both early and late after transplantation. Transplants were harvested up to 19 months later for histologic and mechanical analyses. In all dogs, BMSC transplants formed significantly greater amounts of bone over their control counterparts. The new bone formed an extensive union with the underlying mandible. BMSC transplants retained the majority of their initial volume, while control (HA/TCP only) transplants were nearly completely resorbed. By qCT, the extent of newly formed bone could be determined non-invasively. In summary, HA/TCP particles alone undergo a high degree of resorption, while autologous cultured BMSC-HA/TCP transplants provide long-term bony augmentation of the mandible.