Oxygen permeability measurements of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) disk shaped membranes fabricated by thermoplastic processing and sintered at different temperatures (1000–1100 °C), showed no influence of the grain size on the oxygen permeation fluxes. To further investigations, Electron Backscattered Diffraction (EBSD) and Conductive mode (CM) microscopy methods were used for texture analysis and observation of the local electrical behavior in the BSCF membranes, respectively. EBSD results revealed that the grain size of the membranes increased with increasing the sintering temperature from an average of 3.32 μm at 1000 °C to 18.25 μm at 1100 °C. Also, it was seen that there was no textural difference between the different samples. CM analysis demonstrated that the electronic conductivity of the grains and grain boundaries was similar in the membrane sintered at 1000 °C. Finally, the stability of the membrane under the operation conditions was tested, and it was found that the permeation flux was nearly constant at 900 °C after an operation time of more than 50 h, whereas oxygen permeation flux declined after a relative short time at 825 °C.