Preheat oven to 500. Coat a nonstick skillet with cooking spray. Add sausage and flatten with a spoon. Cook over medium high heat, breaking up sausage with a wooden spoon into small pieces, until browned, about 5 minutes.
Drain sausage on paper towels. Wipe out skillet if necessary.
Coat skillet with cooking spray; heat over medium high heat. Add green and red bell peppers, onion and garlic. Coat vegetables lightly with cooking spray.
Cook, stirring often, until crisp-tender, about 5 minutes. Stir in oregano and pepper flakes.
Spread tomato sauce over crust. Top with vegetable mixture. Dot with sausages and sprinkle cheese over everything.
Bake pizza for about 12 minutes, until crust is golden. Slide pizza onto a large cutting board. Let rest for 5 minutes before serving. Cut into wedges and serve.