In order to investigate the effect of the microstructure on the oxygen permeation in Ba0.95La0.05FeO3-delta membranes, three different methods such as solid-state reaction, nitrate and acetate decomposition (NAD), and amorphous malic acid precursor (AMP) methods were used to fabricate membranes with different grain sizes. The grain size of the membranes was successfully controlled from 35 to 829 mu m2 via sintering at 1175 degrees-1275 degrees C. The oxygen permeation fluxes through the Ba0.95La0.05FeO3-delta membranes increased with a decrease in the grain size. The AMP method, using malic acid as a complexing agent, produced a membrane having the highest oxygen permeability (3.10 cm3 center dot(min center dot cm2)-1 at 930 degrees C) and the smallest grain size. The results obtained again confirmed the significant importance of microstructure control in designing high-performance oxygen permeable membranes.