Preheat oven to 350 F. Coat the pan with cooking spray and set aside.
In a large, non-stick skillet heat the oil over medium-high. Add onions to the skillet and sauté 3 minutes, or just until the onion is tender and translucent. Set aside.
In a large mixing bowl, combine the flour, baking soda, and salt. Make a well in the center of the mixture.
In a medium mixing bowl combine the buttermilk, butter, and egg whites mixing well with a wire whisk. Add the buttermilk mix to the flour, and stir just until ingredients are moist. Fold in the onion, olives, parsley and oregano.
Pour the batter into the prepared loaf pan and bake at 350 F for 45 – 50 minutes, or until a wooden pick inserted in the center comes out clean.
Cool in pan on a wire rack for 10 – 15 minutes. Remove from pan and allow to cool on the rack another 15 minutes before slicing.