This work is focused on phase development of silicon oxycarbide (SiOC) nanocomposites during flash pyrolysis. Three important variables evaluated are applied electric field, current limit, and pyrolysis temperature. They significantly facilitate the microstructure evolution of SiOC and cause the formation of more ordered carbon and SiC phases at>640 degrees C lower temperature than the typical pyrolysis process. With the increase in the applied electric field, pyrolysis temperature, and current density, the mass loss is higher, the SiC formation and carbon precipitation are more extensive, and the carbon phase is more ordered. The resulting SiOC samples are stable up to 742 degrees C in air. The fundamental cause is due to the drastically accelerated nucleation rate for both the C and SiC phases from the applied electrical field, through the mechanisms of Joule heating and electromigration. This work provides an accelerated route to synthesize high-temperature SiOC nanocomposites.