Flip the crust over onto the cooler part of the grill and brush with olive oil. Sprinkle one-quarter of the cheese over the crust and top with one-quarter of the peppers, tomatoes, garlic and capers. Move the pizza back to the hot area of the grill to melt the cheese. Cook until the bottom of the crust is lightly charred, about 2 minutes; if it starts to burn, move it to the cooler side. Sprinkle with salt and pepper and serve immediately. Repeat with the remaining dough and toppings to make 3 more pizzas.