This study aimed to compare the dietary supplementation of oleuropein (O) and α-tocopherol acetate (TA) alone or with organic selenium (Se) on liver antioxidant status and some plasma biochemistry parameters in Japanese quails reared under heat stress (HS). A total of 800, two-weeks old quails were kept in wire cages in the temperature-controlled rooms at either 22°C or 34°C for 8 h/d and fed on a basal diet (NC) or the diets supplemented with TA (TA200) or O (O200) at 200 mg/kg alone or with OSe (TA200+OSe and O200+OSe) to the NC diet. HS decreased the total antioxidant status (TAS) and increased the total oxidative stress (TOS) and oxidative stress index (OSI) of liver compared to thermoneutral temperature (TN). The TA200, O200, TA200+OSe and O200+OSe diets increased TAS and decreased TOS of liver compared to those of quails fed NC. OSI was decreased by the TA200, O200 and TA200+OSe diets compared to NC and O200+OSe diets. HS reduced plasma albumin (A) and total protein (TP) concentrations, on the other hand, increased plasma glucose (G), total cholesterol (CHO) and triglyceride (TG) levels compared to TN. The TA200, O200, TA200+OSe and O200+OSe diets reduced plasma total CHO and TG levels and increased plasma A level. The TA200 and TA200+OSe diets reduced plasma G level and increased plasma TP levels compared to those of quails fed the other diets. In conclusion, dietary supplementation of vitamin E and oleuropein alone or with organic selenium is necessary to remove the negative effects of heat stress on liver antioxidant status and some plasma parameters of quails.