Mixed ionic and electronic conductors (MIEC) have presented great economical and environmental interests for these last years because of their potential applications for electrode materials in solid oxide fuel cell and for oxygen separation form air such as in catalytic membrane reactors for methane conversion into syngas (H-2-CO mixture) (A.F. Sammells, M. Schwartz, R.A. Mackay, T.F. Barton, D.R. Peterson [1], U. Balachandran, J.T. Dusek, R.L Mieville, R.B. Poeppel, M.S. Kleefisch [2], H.J.M. Bouwmeester, B.A. Boukamp [3]). A good compromise between oxygen permeability, chemical stability and physical properties is required to optimize the process. La(1-x)SrxFe(1-y)GayO3-delta materials fulfill this requirement and were retained as membrane for catalytic membrane reactor (CMR) (Y. Teraoka [4], G. Etchegoyen, T. Chartier [5]). Oxygen semi-permeations through La(1-x)SrxFe(1-y)GayO3-delta membranes have been measured under various oxygen partial pressure gradients from 973 K to 1273 K, and compared with the values obtained by isotopic oxygen exchange depth experiments (S. Kim, S. Wang, X. Chen, Y.L Yang, N. Wu, A. lgnatiev, A.J. Jacobson, and B. Abeles [6]). Those results lead to a better understanding of the oxygen transport through the membrane and the influence of Sr and Ga amounts on oxygen semi-permeation through the membrane. The influence of Ga amount is not limited to the improvement of dimensional stabilities but it also increases oxygen diffusion and surface exchange kinetic. This paper suggests that La0.6Sr0.4Fe0.6Ga0.4O3-delta perovskite is a very good compromise for membrane reactor materials and opens new perspectives on membrane architecture development. (C) 2010 Elsevier B.V. All rights reserved.