01 - Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
02 - Evenly distribute the prepared bagel pieces across the bottom of the greased baking dish.
03 - Drizzle half of the pizza sauce over the bagel layer. Follow this with half of the shredded mozzarella and grated Parmesan cheeses.
04 - Add half of the pepperoni, black olives, diced bell pepper, and thinly sliced red onion over the cheese. Sprinkle with half of the dried Italian herbs.
05 - Repeat the layering process with the remaining pizza sauce, cheeses, toppings, and Italian herbs to create a balanced, layered effect.
06 - Cover the baking dish loosely with aluminum foil. Place in the preheated oven and bake for 20 minutes.
07 - Remove the aluminum foil. Continue to bake for an additional 10 minutes, or until the cheese is thoroughly melted, bubbly, and lightly golden brown.
08 - Allow the casserole to rest for 5 minutes before serving. Optionally, garnish with fresh chopped basil or parsley.