Preheat the oven to 375 degrees F (190 degrees C).

Rub oregano and basil over chicken breasts.

Spray a large skillet with cooking spray and heat over medium-high heat. Add garlic; cook and stir until fragrant, 2 to 3 minutes. Add chicken; cook until browned and no longer pink in the center, about 5 minutes per side.

Pour half of the spaghetti sauce into a large baking dish. Lay chicken breasts on top. Coat chicken with remaining spaghetti sauce. Scatter mozzarella cheese over sauce. Arrange 6 pepperoni slices over each chicken breast.

Bake in the preheated oven until cheese is melted, about 10 minutes.