Preheat the oven to 425°F (220°C). Lightly grease a quarter sheet pan (approximately 9 x 13 inches) with olive oil.
In a large skillet, heat 1 tablespoon olive oil over medium heat. Add the Italian sausage, breaking it up with a spoon, and cook until browned and cooked through, about 6-8 minutes. Remove sausage from skillet and set aside.
In the same skillet, add the sliced red, green, and yellow bell peppers and sliced onion. Season with salt, black pepper, and crushed red pepper flakes. Sauté until vegetables are tender and slightly caramelized, about 5 minutes. Remove from heat.
Roll out the pizza dough on a lightly floured surface to fit the quarter sheet pan. Transfer the dough to the prepared pan and gently press it to the edges.
Spread the pizza sauce evenly over the dough, leaving a small border around the edges.
Sprinkle half of the shredded mozzarella cheese over the sauce.
Distribute the cooked sausage evenly over the cheese layer.
Top with the sautéed bell peppers and onions.
Sprinkle the remaining mozzarella cheese and grated Parmesan cheese evenly on top.
Sprinkle dried Italian seasoning over the pizza.
Bake in the preheated oven for 15-20 minutes, or until the crust is golden and the cheese is melted and bubbly.
Remove from the oven and let cool for 5 minutes before slicing and serving.