Cook the beef and oregano in a 10-inch skillet over medium-high heat until the beef is well browned, stirring often to break up the meat. Pour off any fat.
Stir the picante sauce, tomato sauce and corn in the skillet. Cook until the mixture is hot and bubbling. Stir in the cheese. Pour the beef mixture into a 2-quart shallow baking dish.
Mix the corn muffin mix according to the package directions. Spread the batter over the beef mixture.
Bake at 375°F. for 25 minutes or until the crust is golden brown. Let stand for 10 minutes before serving.