Single phase, cubic perovskites of composition La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Al, Ga, Cr, Ti, Ta and Nb, were prepared by spray pyrolysis from aqueous precursor solutions. The effect of B-site substitution on the stability in a H2 containing atmosphere was investigated using temperature programmed reduction (TPR). High temperature X-ray diffraction (HT-XRD) was performed under conditions similar to those in the TPR experiments. La0.2Sr0.8FeO3 − δ forms a brownmillerite-type anion-deficient ordered perovskite upon reduction at T ≈ 500. B-site substitution suppresses oxygen vacancy ordering, maintaining a perovskite structure under the above reducing conditions up to T ≈ 700 °C. Trends in the kinetics of decomposition of B-site substituted La0.2Sr0.8FeO3 − δ are discussed.