The structures of La 4 BaCu 4 NiO 1 3 . 2 0 and La 4 BaCu 4 CoO 1 3 . 3 5 oxides synthesized in NaOH-KOH flux at 450 o C were studied using powder neutron diffraction Rietveld analysis. These oxides crystallize in a tetragonal structure in the P4/m space group with Ni 3 + or Co 3 + partially occupying 6-coordinated (1a) and 5-coordinated (4j) sites of the La 4 BaCu 5 O 1 3 + δ system. Increase in oxygen content with Ni and Co substitution is reflected in the increase in unit-cell volume, compared with that of the parent La 4 BaCu 5 O 1 3 + δ .