Casserole Italiano

1/2 cup chopped onion
1/2 cup chopped green bell pepper
1/4 cup butter
1 1/2 pounds ground round
1 1/2 teaspoons salt
1/4 teaspoon pepper
1/2 teaspoon oregano
2 tablespoons Worcestershire sauce
1 (8 ounce) package elbow macaroni,
    cooked according to directions
1 (3 ounce) can button mushrooms, drained
1 can tomato soup, undiluted
1 medium tomato, chopped
1/2 cup grated Parmesan cheese

Preheat oven to 375 degrees F.

In a large skillet, saut