The effect of Be concentration on the formation of CdSe self-assembled quantum dots grown on Zn1-xBexSe by molecular-beam epitaxy has been investigated using photoluminescence, atomic force microscopy, contactless electroreflectance, and surface photovoltage spectroscopy. Systematic decrease of the quantum dot (QD) size by increasing the Be concentration (x) in the Zn1-xBexSe barrier layer has been demonstrated. A 233 meV blueshift in the photoluminescence emission energy was obtained by changing the Be concentration of the barrier layer from x=0.02 to x=0.24. A corresponding decrease in the size of uncapped QDs was observed. Furthermore, a significant effect of unintentional variation in growth parameters on the size of the QDs was also evident. This suggests that very careful control of the growth conditions is essential in order to utilize this phenomenon for practical applications.