The current research takes advantage of thermodynamic modelling results to tune the microstructure and regional compositions of (La0.8Sr0.2)0.98CrxFe1-xO3±δ (x=0.3, 0.5, 0.7) in the purpose of enhancing its oxygen transport membrane (OTM) properties. The samples are synthesized by sol-gel method, annealed, and heat treated under reducing atmospheres above 1000ᵒC. The microstructure and changes in regional compositions have been characterized by scanning electron microscopy and Energy-dispersive X-ray spectroscopy. Based on the modelling results, different oxygen partial pressure and temperatures have been chosen to improve densification of the samples and dissolve detrimental secondary phases into the perovskite structure. The quality of the tuning process has been measured by thermodynamic modelling and X-ray diffraction. The results show that the tuned samples can have reliable requirements for OTM application with higher densification, reliable chemical stability, and promising electrical and thermal properties.