There is provided a process for converting methanol and/or dimethyl ether to a product containing C.sub.2 to C.sub.4 olefins which comprises the step of contacting a feed which contains methanol and/or dimethyl ether with a catalyst comprising a porous crystalline material. The contacting is conducted in the presence of a cofed aromatic compound under conversion conditions including a temperature of about 350.degree. C. to about 550.degree. C. and a methanol and/or dimethyl ether partial pressure less than or equal to 50 psia (345 kPa). The porous crystalline material used in the catalyst has a pore size greater than the critical diameter of the aromatic compound and a Diffusion Parameter for 2,2-dimethylbutane of about 0.1 to about 26 sec.sup.-1 when measured at a temperature of 120.degree. C. and a 2,2- dimethylbutane pressure of 60 torr (8 kPa), and the aromatic compound is capable of alkylation by the methanol and/or dimethyl ether under said conversion conditions.