Heat in the oil in a large saucepan over medium high heat. Crumble in the ground beef and cook until no longer pink, using a spoon to break up the meat. Add in the onions and cook for another 5 minutes, until onions are softened. Stir in the garlic, Italian seasoning, salt, and pepper, and cook for 2 minutes. Pour in the tomato sauce and crushed tomatoes and bring to a low simmer. Cover and simmer for 30 minutes.
While the sauce cooks, preheat oven to 375 degrees. Boil the penne short of 2 minutes of the recommended cooking time so that it is very al dente. Drain the pasta. In a large bowl, combine the pasta, meat sauce, parmesan, and 1 ½ cups of mozzarella. Toss to combine and pour into casserole dish or 9 x 13 baking pan. Top with the remaining ½ cup of mozzarella cheese.
Cover with foil and bake for 30 minutes until bubbly. If desired, broil for 2-3 minutes to brown top slightly. Let sit for 5 minutes before serving.
Notes
Prepare ziti up to a day in advance and bake prior to serving. Add 10-20 minutes to baking time to ensure that the ziti is properly heated through.