Pat the venison dry. Cut bell peppers into quarters, trim, rinse and chop. Clean shiitake mushrooms and cut into smaller pieces or cut in half, depending on size. Rinse orange in hot water and slice off half of the peel. Cut orange peel into thin strips.
Peel onion and chop finely. Heat oil in a Dutch oven. Add venison and onion and sauté until browned. Add bell peppers and shiitake mushrooms and sauté briefly. Squeeze juice from orange. Add orange strips and orange juice to the Dutch oven, season with soy sauce and pepper and pour in the game stock. Cover and simmer for 1 ¼ - simmer 1 ½ hours.
Stir in cornstarch and bring to a boil, stirring constantly. Season with salt and pepper and serve sprinkled with parsley.