2 pounds ground beef 1 large onion, chopped 2 garlic cloves, minced 1 jar (24 ounces) spaghetti sauce 1 can (14-1/2 ounces) diced tomatoes, undrained 1 can (4 ounces) mushroom stems and pieces, drained 1 teaspoon Italian seasoning 3 cups uncooked medium pasta shells 3 plum tomatoes, sliced 3/4 cup shredded provolone cheese 3/4 cup shredded part-skim mozzarella cheese

In a large skillet, cook beef and onion over medium heat until no longer pink. Add garlic; cook 1 minute longer. Drain. Stir in spaghetti sauce, diced tomatoes, mushrooms and Italian seasoning. Bring to a boil. Reduce heat; simmer, uncovered, 20 minutes.
Meanwhile, preheat oven to 350°. Cook pasta according to package directions; drain. Add to beef mixture and gently stir in tomatoes.
Transfer to an ungreased 13x9-in. baking dish. Sprinkle with cheeses. Bake 25-30 minutes or until bubbly and heated through.