Nanostructured ceramics with La1-xSrxGa1-yMgyO3-delta composition have been processed by spark plasma sintering of precursors obtained by mechanosynthesis. The compositions with x=0.10 and y=0.20 are single-phase ceramics even at the lowest processing temperatures of 900 degrees C. For x=0.20, y=0.17, typical secondary phases as SrLaGaO4 and SrLaGa3O7 appear at all the processing temperatures, from 900 degrees to 1100 degrees C. The high reactivity of the precursors due to the prolonged milling allows highly densified ceramics (> 98%) to be obtained at moderate applied pressures (100 MPa), and at temperatures for which the nanostructure scale is maintained. Single-phase ceramics present higher conductivity than those with isolating secondary phases. The nanostructure appears to break the vacancies ordering, and the conductivity is produced through random vacancies paths, diminishing the activation energy and increasing the total conductivity of the ceramics.