Preheat the oven to 400ºF. In a small bowl, stir together the Italian seasoning blend, garlic powder, salt, and olive oil.
Place the chicken breasts on a cutting board and cover with a piece of plastic wrap to prevent splatter. Use a mallet or rolling pin to pound the chicken to an even thickness, about 3/4-inch thick. Cut each chicken breast in half to make two equal sized pieces.
Place the chicken breasts in a shallow baking dish or on a baking sheet, making sure they have at least an inch of space around them. Spread the oil and herb mixture over the surface of each piece of chicken.
Bake the chicken in the fully preheated 400ºF oven for 15 minutes. While the chicken in baking, slice the mozzarella.
After 15 minutes, remove the chicken from the oven. Spread 1 Tbsp pizza sauce over the surface of each piece. Next top each piece with about 1oz. mozzarella and two slices of pepperoni.
Return the chicken to the oven and bake for 5-7 minutes more, or until the internal temperature of the chicken reaches 165ºF. Remove from the oven and serve.