Massive uncontained glenoid defects are a difficult surgical problem requiring reconstruction in the setting of either primary or revision total shoulder arthroplasty. Our aim is to present a new one-stage technique that has been developed in our institution for glenoid reconstruction in the setting of massive uncontained glenoid bone loss. We utilise a modified delto-pectoral approach to perform our dual biology allograft autograft glenoid reconstruction. The native glenoid and proximal femoral allograft are prepared and shaped to create a precisely matched contact surface, which permits axial compression to secure fixation. The surface of the glenoid is lateralised to at least the level of the coracoid. The central cancellous femoral allograft is removed and impaction autografting is performed prior to implantation of a glenoid base plate with 25-mm long centre peg. Two screws are inserted into the best quality native scapular bone available to ensure compression. A reverse shoulder arthroplasty is implanted. We have performed our dual-biology reconstruction of the glenoid in combination with reverse total shoulder arthroplasty in 8 patients to date. The technique has been performed in the setting of massive uncontained glenoid defects without prostheses as well as in revisions from failed hemiarthroplasties and total shoulder arthroplasties. Our post-operative follow-up is now up to 32 months. CT scanning as early as 6 months demonstrates incorporation of the graft. There has been no evidence of loosening. None of our cases have been complicated by infection or peri-prosthetic fracture and there have been no dislocations. One patient sustained an acromial stress fracture at 9 months post-operatively after lifting a 100-pound gas cylinder. This was diagnosed on bone scan, had no impact on the construct and was managed in a sling for comfort. Another patient has developed Nerot grade I notching which substantially in all patients, with an average improvement of 6.6 on a 10-point scale. Our dual biology allograft-autograft reconstruction is a useful and elegant technique in the setting of massive uncontained defects of the glenoid, which permits the implantation of a reverse total shoulder arthroplasty. We believe this technique to be reproducible and uses materials that are both readily available and familiar.