Step 1: Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
Step 2: Heat olive oil in a large skillet or Dutch oven over medium-high heat. Add the ground beef and chopped onion. Cook, breaking up the beef with a spoon, until the beef is browned and the onion is softened, about 8-10 minutes. Drain any excess fat.
Step 3: Stir in the minced garlic, Italian seasoning, salt, and black pepper. Cook for another minute until fragrant.
Step 4: While the beef is cooking, bring a large pot of salted water to a rolling boil. Add the penne or ziti pasta and cook according to package directions until al dente (firm to the bite). Drain well and set aside.
Step 5: In a large bowl, combine the cooked ground beef mixture, drained pasta, both jars of Alfredo sauce, milk, and ½ cup of grated Parmesan cheese. Mix thoroughly until everything is well combined and coated.
Step 6: Spread half of the pasta mixture evenly into the prepared baking dish. Sprinkle with 1 cup of shredded mozzarella cheese.
Step 7: Top with the remaining pasta mixture, spreading it out evenly. Sprinkle the remaining 1 cup of shredded mozzarella cheese over the top.
Step 8: Bake for 25-30 minutes, or until the cheese is melted, bubbly, and lightly golden brown. If desired, you can broil for the last 1-2 minutes for extra browning, watching carefully to prevent burning.
Step 9: Remove from oven and let stand for 5-10 minutes before serving. Garnish with fresh parsley and extra Parmesan cheese, if desired. Enjoy your delicious cheesy beef alfredo bake recipe!