Preheat the oven to 375° F.
Spray a 9x11 or 9x13 casserole dish with non-stick olive oil spray.
Start by slicing the chicken breasts into 3 thin cutlets.
Mix the garlic powder, onion powder, dried oregano, salt, and pepper into a small bowl until combined.
Layer the marinara sauce into the baking dish, then top with the sliced chicken breasts. Drizzle with olive oil, then season with garlic powder, onion powder, oregano, salt, and pepper.
Top with additional marinara sauce, pepperoni, shredded cheese, sliced onions, olives, minced garlic, and additional pepperoni.
Cover with foil and bake for 35 minutes. Uncover and bake for 5 more minutes until the cheese is melted and gooey. The chicken is done when it registers 165° internal temperature when measured with an internal thermometer.
Top with fresh chopped basil or parsley and serve.