Prepare rice according to package directions. Preheat oven to 350F.
Cut out stem ends of bell peppers and discard. Scoop out seeds. Bring water to a boil in a large pot and blanch the peppers until tender-crisp, about 1 minute. Drain and cool under cold running water. Set aside.
Heat oil in a large nonstick skillet over medium heat. Add onion and garlic and cook, stirring occasionally, until softened, about 3 minutes. Add turkey and cook, crumbling with a wooden spoon, just until it loses its pink color, about 2 minutes. Drain the fat.
Transfer the turkey mixture to a medium bowl and mix in rice, half of the tomato sauce, parsley, salt (if using) and pepper. Stuff the peppers with the mixture and place in a 2-quart casserole dish. Spoon the remaining half of the tomato sauce over the peppers. Cover and bake until the peppers are tender and the filling is heated through, 30 to 35 minutes.