The effect of microwave processing on the high temperature oxidation behavior of AlCrTiTaMo equimolar composition was investigated. The long term oxidation studies were carried out at 900 °C and 1100 °C for 100 h. Oxidation kinetics of the microwave-processed alloy yields a significant decrease in the oxidation rate and mass gain compared to the as-cast alloy. The physical nature and stability of thermally formed oxide on the as-cast and processed samples were probed using long-term electrochemical impedance spectroscopy (EIS) studies. The impedance of the oxide formed on the as-cast alloy decreased with the immersion time while it continuously increased for the microwave processed alloy suggesting its stable and defect free nature. The superior oxidation behavior of microwave-processed alloy was attributed to microstructural homogenization leading to the formation of protective oxide layer with favorable chemistry and structure. © 2021 Elsevier B.V.