Small amounts of manganese oxide incorporated on MgO enhanced C-2+ hydrocarbon selectivity during the oxidative coupling of methane (OCM). Both C-2+ selectivity and CH4 conversion were also improved by adding alkaline metal halides. Dosing CH2Cl2 pulses into the CH4/O-2 feed stream over alkali promoted Mn-MgO catalysts led to an improvement in the yield to C-2+ hydrocarbons. The extent of this effect and the stability of the alkali phases were found to depend on the type of promoter. Photoelectron spectroscopy (XPS) revealed that all the used catalysts retained important amounts of chlorine in the form of Cl- ions, and simultaneously manganese was oxidized to Mn4+. In the light of quantitative XPS data, a redox mechanism consisting of the decomposition of halocompound at catalyst surface through formation of an oxyhalide of the type MnO2-x/2Clx has been proposed. The different patterns for CH4 conversion and C-2+ selectivity indicate a key role of the alkali promoter and its distribution on the surface, on the formation of this Cl-containing species.