In this paper we report on the growth and characterisation of CdSe quantum dots grown by MBE on a MgS-rich ZnMgSSe barrier and characterized by 77K PL and 4K µ-PL. The dot density was estimated to be approximately 1010 cm-2 however some emission lines were sufficiently well resolved to investigate their behaviour individually; their emission was observed to change both in intensity and energy, showing a high frequency random jittering. Correlation of the dot intensity over much longer time periods (~200s) was also observed. These results will be compared with previous results from CdSe dots grown on ZnSe barriers. © 2010 IOP Publishing Ltd.