Heat the olive oil in a large saute pan and add the onions, radishes, salt and pepper.Saute the onions and radishes on medium heat for 5 minutes or until softened.Add the oregano, garlic powder, and corned beef to the pan and stir well until combined.Cook over low to medium heat, stirring occasionally for 10 minutes or until the radishes are soft and starting to brown.Press the mixture into the bottom of the pan and cook on high heat for 2-3 minutes or until the bottom is crisp and brown.Serve hot.