Preheat oven to 350º. Place bread on a rimmed baking sheet and toast until dry and beginning to turn golden, 10-12 minutes. Transfer bread to a large bowl and add tomato, mozzarella, pepperoni, basil, peppers, parsley, oil, and vinegar.
Toss to combine and season with salt and pepper. Bread will soften as it absorbs tomato juices, oil, and vinegar.