The objective of this paper was to asses the oxidative stability of cold pressed rapeseed and sunflower oils with the addition of natural antioxidant, oregano extract, using the Rancimat and Schaal Oven tests. Fresh, cold pressed rapeseed and sunflower oils were the investigation material. The oils were stabilized by adding the oregano extract, a natural antioxidant in the form of an ‘Origanox’ commercial preparation, in the doses of 500, 1000, and 1500 mg/kg. The general quality of oils was estimated (acid value, peroxide value, anisidine value, Totox index, and iodine value). The oxidative stability of oils containing the antioxidant applied was determined using a Rancimat test at a temperature of 120ºC, and, at the same time, a Schaal Oven test was performed at a temperature of 63 °C. The antioxidant activity of the oregano extract depended on the quantity of its dose applied. As for the cold pressed rapeseed oil, the bigger this dose was, the longer was its induction time. The 1500 mg/kg dose of oregano extract proved to have the highest efficiency in the cold pressed rapeseed oil. As for the cold pressed sunflower oil, a pro-oxidative effect of the extract added was found using both the Rancimat and the Shaal Oven tests.