We have demonstrated continuous wave operation of BeZnCdSe quantum well laser diodes at room temperature in the green to yellow spectrum range. The laser diodes structures were grown by molecular beam epitaxy. To overcome low doping ability of a p-cladding layer materials of BeMgZnSe, a short-period superlattice of BeMgZnSe/ZnSe:N was employed. High-power lasing over 50mW at a peak wavelength of 536 nm was achieved. By employing highly strained BeZnCdSe quantum wells, continuous wave lasing up to 570 nm has been also achieved. The threshold current density of 20-μm-wide lasers was found to be sufficiently low (less than 0.85 kA/cm 2 ) in the wavelength range of 545 nm to 570 nm.