The BaO-BaO2 reaction cycle was investigated in a range of temperatures from 973 to 1123 K and oxygen pressures from 0 to 0.2 MPa using the BaO2-MgO oxygen acceptor of different barium content and sample size prepared with barium peroxide and magnesium oxide. The rates of the oxidation of barium oxide and the reduction of barium peroxide by the BaO2-MgO oxygen acceptor during repeated cycling were little influenced by pellet sizes smaller than 16 mm in diameter, and an increase in the barium content of the sample led to a decrease in the reaction rate, while oxygen loading of the oxygen acceptor increased. In addition, fairly high reaction rates were obtained for the BaO2/MgO at ratios up to 1:1.4 (mol). The application of the BaO-BaO2 reaction cycle to oxygen production or enrichment with regard to operation mode and conditions was also investigated using the BaO2-MgO oxygen acceptor.