The production of La0.95Sr0.05Ga0.90Mg0.10O3-δ powders was achieved at room temperature by a mechanosynthesis route in a high energy planetary ball mill starting from a mixture of lanthanum, strontium, gallium and magnesium oxides. The milling was carried out in nylon containers, using zirconia balls and a balls:powder mass ratio of 10:1. The planetary rotation was kept constant at 650 rotations per minute (rpm), and the container at 1300 rpm, in the opposite direction. The formation of the perovskite phase was detected from the early milling stages and nearly completed after milling for 360 min, as shown by powder X-ray diffraction. Transmission electron microscopy results revealed that powders consist of agglomerates of homogeneous, crystalline particles with an average equivalent diameter of about 16-17 nm, in excellent agreement with average crystallite size estimates obtained from X-ray diffraction.