We report design, MBE growth and optical studies of optically dense, strained ZnSSe/ZnCdSe multiple quantum wells (MQWs) and superlattices (SLs). To avoid stress relaxation in the thick multilayer structures, particular attention is paid to the accurate design of alternating compressive and tensile stress in the constituent layers. The feasibility of using the alternatively strained SLs and MQWs as the guide and active regions of optically pumped MgZnSSe/ZnCdSe blue-green lasers is experimentally confirmed. A room-temperature threshold power density as low as 20 kW/cm2 has been achieved at 490 nm in conventional waveguide-geometry lasers with a SL guide layer. A room-temperature optically pumped vertical-cavity laser utilizing a long ZnSSe/ZnCdSe MQW active region and a short external cavity is demonstrated.