Optical emission is reported from an n-channel GaAs/AlGaAs bistable field effect transistor (BISFET). This emission is found to be strongly correlated with the gate current flowing in the device. Abrupt transitions, referred to as optical switchup and switchdown, are observed in the optical output characteristics as the drain bias is varied, with a switching ratio in excess of 20 dB. These transitions correspond with those seen in the drain and gate currents as the feedback loop from gate to source switches on and off. The transitions exhibit large hysteresis, corresponding to that seen in both the drain and complementary transfer characteristics of the device. The drain voltage at which the optical transitions are observed, and the associated hysteresis, are found to be very sensitive to gate bias, particularly in the saturation region of operation. Implications of the optical characteristics for the carrier flow mechanisms within the BISFET are discussed. Methods of increasing the optical output efficiency of the device are described.