Purpose: Reports remain sparse on the outcomes of quadratus femoris muscle pedicle bone grafting (QF-MPBG) for osteonecrosis of the femoral head (ONFH) in the existing literature. This study reports on the clinico-radiological outcomes of this procedure in early-stage non-traumatic ONFH using a quadriceps-coxae sparing (QCS) modified posterior approach. Materials and Methods: This prospective study included 22 symptomatic patients suffering from early-stage, non-traumatic ONFH. These patients underwent QF-MPBG surgery using a QCS modified posterior approach and were followed up for a minimum duration of 24 months. Results: The mean age of patients was 29 years (range, 20-47 years). As per the modified Kerboul’s combined necrotic angle, the distribution of patients was as follows: grade 1 (n=5); grade 2 (n=9); grade 3 (n=4); and grade 4 (n=4). All four patients belonging to grade 4 and two belonging to grade 3 required total hip arthroplasty (THA) within 24 months. As per the modified Ficat’s classification, 18 cases were in stage II and four in stage I. Six cases (out of the preoperative 18 cases classified as stage II) deteriorated to stage IV, and two deteriorated to stage III. The mean Harris hip score improved from 63 (range, 57-67) to 75 (range, 50-93) after surgery (P<0.05). Four out of six patients necessitating THA had steroid-induced ONFH. Conclusion The QCS modified posterior approach provides sufficient exposure required for QF-MPBG. Steroid-induced ONFH and a modified Kerboul’s combined necrotic angle of >250° may be considered as potential risk factors for progression of this disease.