n onion peeling machine was designed, manufactured, developed and evaluated to suit the small and medium processing units. The onion peeling machine consists of seven parts, main frame, peeling drum, inlet and outlet openings, collection basin, water and air supplying systems, and power transmission. The machine was evaluated using different onion bulb sizes (small, medium & large). A mixed sample of different sizes was also tested. The evaluation process was conducted under three different drum rotational speeds (30, 40 and 50 rpm), three different peeling residence times (1, 2 and 3mins) and three different batch loads (18, 24 and 30kg). The optimum peeling efficiency of 74.9, 65.24, 80.08 and 85.45% were obtained at 24kg batch load (0.36 ton/h.), 2min peeling residence time and 40 rpm for small, medium, mixed and large sizes respectively. Water pump and air compressor were added to the peeler to improve the peeling efficiency, and it was tested under the previous conditions. The corresponding values of peeling efficiency for the machine with pump water at water pressure of 400kPa were 76.73, 83.06, 99.20 and 87.49 %, respectively. While they were 76.33, 72.87, 87.530 and 88.37%, respectively for air pumping at pressure of 500kPa. The estimated costs of onions peeling machine were 28.47, 29.56 and33.75 L.E/ton for the machine only, machine with water pump and machine with air compressor respectively. These values of estimated costs using the developed machine are very competitive with the cost of manual peeling process which approached about 75 L.E/ton.