In a small skillet, saute onion in oil until tender. Add oregano and garlic; cook 1 minute longer. Add spinach; cook 3 minutes longer or until liquid is evaporated. Transfer spinach mixture to a large bowl; cool., Add feta cheese and eggs to spinach mixture; mix well. Unfold puff pastry. Spread each sheet with half the spinach mixture to within 1/2 in. of edges. Roll up jelly-roll style. Cut each into twelve 3/4-in. slices. Place cut side down on greased baking sheets., Bake at 400° for 18-22 minutes or until golden brown. Serve warm.