Eggplant Sloppy Joe

Name: Eggplant Sloppy Joe
Ingredients: 1½ lbs. lean ground beef; 1 tablespoon olive oil; 1 cup diced onion; 2 cloves garlic, minced; 2 cups diced eggplant (from one small eggplant, peeled); 2 cups diced button mushrooms (a 10 oz. package); 1 teaspoon salt; ½ teaspoon ground black pepper; ½ teaspoon garlic powder; ¼ teaspoon oregano; 28 oz. can tomato sauce; 2 tablespoons brown sugar; 1 tablespoon worcestershire sauce