Preheat oven to 375 degrees.
In a large skillet, heat the olive oil over medium heat. Add the zucchini and onion and cook until tender, about 5-6 minutes, stirring occasionally. Add the crushed red pepper, garlic, basil, oregano, salt and pepper and cook for one minute more. Set aside.
In a large bowl, combine the oatmeal, egg, onion mixture, turkey and shredded cheese. Mix with your hands. Add the chicken broth and mix again so that the broth is incorporated into the meat mixture.
Line a large, rimmed baking sheet with parchment paper or aluminum foil. Place bell peppers, cut side up onto the baking sheet. Liberally fill peppers with turkey stuffing, making sure to tuck the stuffing into the crevices of the pepper. There should be enough stuffing to mound it atop the peppers. Wet your hands with water and even out the turkey mixture with your fingers -- the water prevents your hands from sticking to the turkey mixture.
Place the stuffed peppers into the oven and roast the peppers for 30-35 minutes, until the turkey is cooked through.
Serve peppers with marinara sauce and additional mozzarella and/or parmesan cheese or for a bubbly baked "casserole" pepper -- spread 1/3 cup marinara sauce in the bottom of a baking dish. Place the peppers in the dish and spoon marinara on top of each pepper. Top with a sprinkle of mozzarella and parmesan cheese and heat under the broiler for 3-5 minutes until lightly browned and bubbly. Serve.