Rather than use fresh oregano, try substituting your recipes with fresh marjoram. Why? Because the taste is similar, yet how much antioxidants you get will typically be higher with most sources of marjoram.
ORAC Source
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010