The oxidative coupling of methane over Li/MgO and BaBiO3-x catalysts irradiated by microwaves and classically heated is reported. Enhanced selectivities in C-2(+) products are observed at lower temperatures under microwave conditions, especially with the Li/MgO catalyst. The complex permittivity measurements of BaBiO3-x show that the regeneration of the active oxygen species on the surface is lower under microwave irradiation than classical heating. X-ray diffraction analyses of the catalyst before and after catalytic reaction, when it is classically heated and when it is heated by microwave irradiation, corroborate these results. Therefore, the CH3-carbanions are less oxidated at the catalyst surface under microwave irradiation. On the other hand, the quenching of the output gas probably decreases the oxidation of CH3 degrees radicals in the gas phase when the Li/MgO catalyst is irradiated by microwaves. The quenching of the output gas is a unique consequence of microwave irradiation which heats the catalyst without heating the wall of the reactor.