In 12-inch skillet, cook beef over medium-high heat 5 to 7 minutes, stirring frequently, until beef is brown; drain. Add the pasta sauce and oregano and bring to a boil. Reduce heat to medium-low and simmer, uncovered, for 5 minutes. Add pepperoni slices and olives. Cook for 1 to 2 minutes, until hot. Stir in cheese. Spoon into baking dish.