Chemical looping air separation (CLAS) has emerged as a promising approach to produce high-purity oxygen with lower cost and reduced energy consumption. We conducted a structural and thermodynamic analysis on Sr0.75Ba0.25FeO3−δ (SBF628), Sr0.75Ba0.25Fe0.875Mg0.125O3−δ (SBFM6271), and Sr0.25Ba0.75FeO3−δ (SBF268) as sorbent candidates for CLAS applications. From a comparison with undoped SrFeO3−δ (SF), we confirmed that partial substitution of A- and B-site cations is an effective strategy to optimize their thermochemical properties under economically viable conditions e.g. 400-700 °C and 0.2-0.01 atm O2. Increased Ba:Sr ratio in the A-site lowered reaction enthalpy and increased oxygen capacity at low temperatures (400-500 °C) while it was also found to correlate well with Fe-O bond length. Under the conditions of 400-600 °C and 0.2-0.01 atm O2, SBF628 achieved the highest oxygen storage capacity of 1.24 wt%. 12.5wt% Mg doping enhanced oxidation kinetics but it didn’t significantly affect the oxygen capacity. Lastly, SBFM6271 and SBF628 demonstrated excellent long-term stability while a small decrease in oxygen capacity (3 wt% on a relative basis) was seen in SBF268 over 100 redox cycles of pressure swing between 0.2-0.01 atm O2 at 600 °C. Our findings identify Ba/Mg substituted SrFeO3-δ as promising oxygen carrier candidates and provide insights that can aid oxygen carrier optimization for CLAS applications.