Preheat your oven to 425°F (220°C).
Heat olive oil in a large skillet over medium heat. Add the Italian sausage, breaking it up with a spoon, and cook until browned and cooked through, about 7-8 minutes. Remove sausage from skillet and set aside.
In the same skillet, add the sliced green, red, and yellow bell peppers along with the sliced onion. Sauté for about 5 minutes until the vegetables are tender but still slightly crisp.
Add dried oregano, crushed red pepper flakes, salt, and black pepper to the peppers and onions. Stir well to combine and cook for an additional 1 minute. Remove from heat.
Lightly grease the quarter sheet pan with olive oil or non-stick spray.
Roll out the pizza dough to fit the quarter sheet pan, pressing it evenly into the corners and edges.
Spread the pizza sauce evenly over the dough, leaving a small border around the edges.
Sprinkle half of the shredded mozzarella cheese evenly over the sauce.
Distribute the cooked sausage evenly over the cheese layer.
Top the sausage with the sautéed peppers and onions mixture.
Sprinkle the remaining mozzarella cheese over the top, followed by the grated Parmesan cheese.
Place the sheet pan pizza in the preheated oven and bake for 15-20 minutes, or until the crust is golden and the cheese is melted and bubbly.
Remove the pizza from the oven and let it cool for 3-5 minutes.
Garnish with fresh basil leaves if desired, slice, and serve warm.