Tricolor-Salad Pizza

Preheat oven to 450° with a pizza stone or baking sheet set on a rack in lowest position. Drizzle 3 tablespoons oil onto a rimmed quarter-sheet pan (9 by 12 1/2 inches). Stretch dough to edges of pan. Drizzle evenly with 1 tablespoon oil; season with salt and pepper. Top with mozzarella, leaving a 1/2-inch border, then tomatoes, cut-sides up.

Bake in pan on stone until bubbly and crust is golden brown and set on bottom, 20 to 22 minutes. Sprinkle generously with Parmigiano. Whisk together vinegar, oregano, and remaining 2 tablespoons oil in a large bowl; season with salt and pepper. Toss with fennel, radicchio, and arugula to evenly coat. Top pizza with salad; serve immediately with more Parmigiano.