In this study, application of two concentrations (0.03 and 0.06%) of Satureja bachtiarica Bunge essential oil (EO) were examined on oxidative stability of rapeseed oil (RO) during autoxidation and after irradiation with ultraviolet (UV) rays (exposition 30 min) at 60°C. The main compounds of EO extracted by the recently designed ohmic ultrasonic extractor (distillation unit) were identified as thymol (∼30%), carvacrol (∼15%) and caryophyllene oxide (∼12%). Antioxidant activity of EO was compared to butylated hydroxytoluene (BHT) during autoxidation. The UV rays induced oxidation process in RO samples both with and without additives. This effect was more vigorous when irradiation was carried out prior to addition of the additives. It was further established that antioxidant activity of EO was better than BHT in samples treated by UV rays. Moreover, EO was able to reduce the stable free radical 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) with a 50% inhibition concentration (IC50) of 32.5 ± 0.6 µg/mL. The findings show the good potential of EO when it is used as a natural antioxidant in food lipids.