Preheat OvenPreheat your oven to 350°F (175°C).
Cook the Beef MixtureIn a large non-stick skillet over medium-high heat, cook and crumble the ground beef with the chopped onion and garlic until browned. Drain excess grease.
Make the Creamy SauceAdd the spaghetti sauce, 4 ounces of the cream cheese, Italian seasoning, and ½ cup of mozzarella cheese to the skillet. Stir and cook until the cream cheese has fully melted, about 5 minutes.
Combine with PastaStir in the cooked penne pasta until evenly coated with the creamy meat sauce.
Assemble the BakeTransfer the pasta mixture into a greased 8×8-inch baking dish. Dot the top with the remaining cream cheese and sprinkle with the remaining ½ cup of mozzarella.
Bake and RestBake uncovered for 20 minutes, or until hot and bubbly. Let rest for 10 minutes before serving.