Cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the cooked penne pasta, marinara sauce, half of the mozzarella cheese, pepperoni slices, green bell pepper, black olives, diced red onion, Italian seasoning, garlic powder, salt, and pepper. Stir well to ensure everything is evenly coated.
Transfer the pasta mixture into a greased 9x13 inch baking dish.
Top the pasta with the remaining mozzarella cheese, spreading it evenly across the top.
Bake in the preheated oven for about 25-30 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes before garnishing with fresh basil leaves.
Serve warm and enjoy your delicious cheesy pizza pasta bake!
Notes
Let it cool slightly before serving for better slicing.