  We have computed with a fine time grid the evolution of the elemental
abundances of He, C, N and O ejected by a young (t < 20 Myr) and massive
(M$=10^{6}$\,\Msun) coeval stellar cluster with a Salpeter initial mass
function (IMF) over a wide range of initial abundances. Our computations
incorporate the mass loss from massive stars (M >30 Msun) during their wind
phase including the Wolf-Rayet phase and the ejecta from the core collapse
supernovae. We find that during the Wolf-Rayet phase (t <5 Myr) the cluster
ejecta composition suddenly becomes vastly over-abundant in N for all initial
abundances and in He, C and O for initial abundances higher than 1/5th Solar.
The C and O abundance in the cluster ejecta can reach over 50 times the solar
value with important consequences for the chemical and hydrodynamical evolution
of the surrounding ISM.
