Preheat the oven to 350 degrees. Cook the rice according to the package directions, and set aside.
Heat the olive oil in a medium saucepan over low heat. Add the garlic and onion, and sauté until translucent. Turn the heat up to medium, and crumble in the turkey meat, separating it as best as you can (it will become easier to separate as it cooks). Sauté the meat until it browns, about 7 minutes. Add salt and pepper, to taste. Once the meat has browned, add 1 cup of chicken broth and the diced tomatoes. Lower the heat and let simmer until the liquid has reduced by half, about 30 minutes.
Add the spinach and stir well. As the spinach is wilting, add the cooked rice. Stir often to marry the flavors and textures. Simmer over low heat for about 20 minutes.
Cut away the tops of the peppers. Discard the ribs and seeds. Add the remaining chicken broth to a baking dish; it should come halfway up the sides. Place each pepper standing up.
Once the stuffing has finished cooking, fill each pepper completely. Top with a layer of bread crumbs or cheese, if desired (this will create a crust when the peppers come out of the oven). Cover the pan with foil, and bake for 35-45 minutes, or when the peppers begin to wrinkle. Serve.