Single crystals of La1−xBaxMn1−yCoyO3 (0.26 ≤ x ≤ 0.37; 0 ≤ y ≤ 0.31) perovskiteswere grown by the flux melt technique using the BaO–B2O3–BaF2ternary system as a solvent. It was found that the cobalt content in the crystals isdetermined by the average oxidized state of the manganese ions and dependsnonlinearly on the molar ratio of Co/Mn in the initial mixture. All the crystalsexhibit ferromagnetic behaviour at low temperatures as well as a jump ofresistivity and a magnetoresistance peak around the Curie temperature, graduallydecreasing as the cobalt content increases. The low-temperature ferromagneticphase transforms from the metallic to the semiconducting state with increase incobalt content.