Baked Penne Pasta Casserole

6 ounces dry penne rigate 1 tablespoon olive oil 1/2 medium yellow onion , diced 1 -2 cup sliced mushrooms 2 -3 minced garlic cloves 1/3 lb ground beef 2[...]

1 lb dry penne pasta , prepared according to package directions 8 ounces lean ground beef 1 onion , chopped 3 garlic cloves , finely chopped 1 (12 ounce) can[...]