Make the compound butter: In a bowl, combine butter, olives and oregano.
Split the bread in half lengthwise. Spread an even layer of compound butter on each cut surface of bread. Reassemble the pieces. Brush the outside of bread with olive oil and season with salt and pepper. Place the bread on the griddle and top with pans or other type of weight to gently press the bread while it is toasting. Griddle or grill for about 4 minutes on each side, or until golden brown.