A 1300 MPa grade engineering steel was processed by a two-stage deformation schedule to investigate the effects of second-stage deformation temperature and strain on transformation behavior, final microstructure, and tensile response. After austenitization, the second deformation step was conducted at 850 and 920 °C with strains of 30% and 50%, followed by controlled cooling. The results show that the influence of temperature depends strongly on strain level. At 30% strain, the higher deformation temperature may promote recovery and reduce defect density, which leads to lower strength but higher ductility. Under the 50% strain condition, the 920 °C deformation condition produces more pronounced microstructural refinement and a higher fraction of high-angle grain boundaries, which contributes to the increase in strength. The strength difference among the tested conditions is mainly related to the combined contributions of grain boundary strengthening and dislocation strengthening, while the retained defect energy also affects recovery-related structural adjustment. Martensite variant analysis reveals that the deformation parameters also change the variant organization in the transformed structure. Among the investigated conditions, the 920 °C-50% sample exhibits the highest strength, while the 920 °C-30% sample shows the best strength–ductility balance, which is related to its moderate strengthening level, relatively low defect-storage state, and characteristic transformed substructure.