The average cycle propylene selectivity of an oxygenate to propylene (OTP) process using one or more fixed or moving beds of a dual-function oxygenate conversion catalyst with recycle of one or more C.sub.4+ olefin-rich fractions is substantially enhanced by the use of selective hydrotreating technology on these C.sub.4+ olefin-rich recycle streams to substantially eliminate detrimental coke precursors such as dienes and acetylenic hydrocarbons. This hydrotreating step helps hold the build-up of detrimental coke deposits on the catalyst to a level which does not substantially degrade dual-function catalyst activity, oxygenate conversion and propylene selectivity, thereby enabling a substantial improvement in propylene average cycle yield. The propylene average cycle yield improvement enabled by the present invention over that achieved by the prior art using the same or a similar catalyst system but without the use of the hydrotreating step on the C.sub.4+ olefin-rich recycle stream is of the order of about 1.5 to 5.5 wt-% or more.