The oxygen-deficient "cubic" perovskite phase SrFe 1- xV xO 2.5+ x (0.05 ≤ x ≤ 0.10) quenched from 1473 K has been investigated by electron microscopy. Samples show a microdomain structure composed of ordered grains less than 20 nm. Oxygen vacancies form a brownmillerite-type superlattice in each microdomain, while six orientation variants have been observed within a particle; the oxygen vacancies in one domain are stringed along one of the six possible <110> C directions of the cubic host lattice. The domain size decreases as x or oxygen content increases. Vacancy arragements within the domains observed in high-resolution lattice images indicate that good structural coherence exists between microdomains and that a basic cubic perovskite skeleton is framed throughout a particle; they also suggest that vacancy content decreases in the boundary regions.