Flash and field assisted sintering techniques (FAST) have been demonstrated in many singular ceramic systems. However, little has been done to thoroughly investigate this phenomenon in binary systems. Zirconia-alumina composites are of interest because of their widespread use in demanding situations for health care, petrochemical and energy applications. The prospect of minimizing grain growth ... [Show full abstract] associated with FAST whilst achieving maximum densification is vital for the above applications to improve performance. Flash sintering behaviour of several zirconia-alumina formulations was investigated under a range of DC electric fields up to 700V.cm−1. At low alumina contents (<10 wt%) the flash behaviour was controlled by the zirconia phase; intermediate compositions (10-70 wt%) show a composite effect; and at high alumina contents (>75 wt%) the effectiveness of field assisted sintering drops off. These pointers allowed to gain further insight into the mechanisms of flash sintering and will help to develop pathways for the adaptation of the technique to process complex ceramic systems.