Dense membranes of mixed-conducting perovskite-type oxides L(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3) and L(0.8)Ba(0.2)Co(0.8)Fe(0.2)O(3) were used for methane coupling by application of pressure-driven O-2 permeation. High operating temperatures, typically above 800 degrees C, were needed to obtain reasonable oxygen fluxes. Conversions were small (1-3%). Both compositions showed comparable C-2 selectivities at low methane partial pressures. At higher pressures the selectivity to C-2 hydrocarbons for Lr0.6Sr0.4Co0.8Fe0.2O3 increased to 67%, whereas La0.8Ba0.2Co0.8Fe0.2O3 showed small C-2 selectivities. Strong surface segregation of Sr and Ba was shown by SEM for bath compositions.