Metal halide perovskites have emerged as promising gain materials for on-chip lasers in photonic integrated circuits (PICs). However, stable continuous wave (CW) lasing behavior under optical pumping at room temperature - a prerequisite for electrically pumped lasing - has not yet been demonstrated. To achieve stable CW operation, we introduce a multiplex of strategies that include morphological, structural and interfacial engineering of CH3NH3PbBr3 (MAPbBr3) thin films to improve perovskite's intrinsic stability, as well as high quality cavity design to reduce the operational power. We demonstrate for the first time, over 90-minute-long green CW lasing with 9.4W/cm2 threshold from a polycarbonate (PC)-defect-passivated, directly patterned MAPbBr3 two-dimensional photonic crystal (PhC) cavity without any substrate cooling. We also show our approach's effectiveness on the performance of MAPbBr3 under electrical excitation: we observe a seven-fold current efficiency enhancement by applying our strategies to a MAPbBr3 LED. This work paves the way to the realization of electrically pumped lasing in perovskites.