Continuous cooling transformation (CCT) behaviour of two transformation induced plasticity (TRIP) steels was investigated using deformation dilatometry. One is an established steel grade with a composition of (mass %) 0.2C, 2Si, and 1.5Mn while the other steel is a novel composition where 2 mass % Al replaces the Si in the former grade. Characteristics of the austenite decomposition during continuous cooling subsequent to thermomechanical processing (TMP) were studied. The effects of accelerated cooling and steel composition on gamma transformation start temperature (Ar-3) phase transformation kinetics and microhardness were investigated. The results show that addition of Al promotes the formation of polygonal ferrite and granular bainite constituents significantly. Furthermore the Ar3 temperature is significantly higher and phase transformation kinetics slower in Al-Mn steel compared to Si-Mn steel. Accelerated cooling increased the hardness and refined the microstructure in both steels. Hardness of Al-Mn steel was found to be lower compared to Si-Mn steel for all cooling rates studied. The results are explained in the context of the influence of composition and thermomechanical processing on microstructural evolution during continuous cooling.