The surface morphology, optical and structural properties of ZnSe epilayers grown on (001) GaAs at 450 degreesC using metalorganic chemical vapor phase deposition are found to be greatly influenced by the initial growth of a thin ZnSe buffer layer at the low temperature of 360 degreesC. Moreover, there is an optimum thickness for the buffer layer on which the quality of the epilayer grown is significantly better, as indicated by four independent quality gauges. In comparison to epilayers grown without a buffer layer, epilayers grows on a buffer layer of optimum thickness around 28 nm show: (1) about 3 orders of magnitude reduction in the density of growth hillocks, (2) narrow line width and about 3 orders of magnitude increase in the intensity of excitonic photoluminescence, (3) much narrower X- ray rocking curve peaks, and (4) mono-layer high surface steps with atomically smooth terraces in between,