A system and process for producing olefins from oxygenate, e.g., methanol or dimethylether, includes a fluidized bed reaction zone that provide contact between the oxygenate and a molecular sieve catalyst such as ZSM-34 or SAPO-34. Improved ethylene selectivity is realized when the oxygenate is stagewise injected into the fluidized bed at one or more locations along the axial direction of the fluidized bed reaction zone.