A process for the production of EPM or EPDM comprising contacting ethylene, propylene, and, optionally, one or more dienes, in a fluidized bed, at a temperature at or above the sticking temperature of the product resin, under polymerization conditions, with a prepolymer, which is not sticky at the process temperature; a cocatalyst; and, optionally, a halocarbon promoter; and, optionally, an inert particulate material, wherein the amount of prepolymer or the combined amount of prepolymer and inert particulate material is sufficient to essentially prevent agglomeration of the fluidized bed and the product resin.