A processing scheme and system for enhanced light olefin production, particularly for increased relative yield of propylene, involves oxygenate conversion to olefins and subsequent oxygenate conversion effluent stream treatment including dimerization of ethylene to butene and metathesis of butenes and/or hexenes with ethylene. The processing scheme and system may further involve isomerization of at least a portion of 1-butene to 2-butene to produce additional propylene.