Abstract: Single phase, cubic perovskites of composition La0.2 Sr 0.8 Fe 0.8 B 0.2 O 3− 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. La0.2 Sr 0.8 FeO 3− 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 La0.2 Sr 0.8 FeO 3− δ are discussed.