Preheat oven to 350 °F.
Combine brown rice and ½ cup water in a small pot and bring to a boil. Turn heat down to low. Cover and cook until water is absorbed, about 30-40 minutes. Fluff with a fork. Cover and refrigerate until completely cooled. A rice cooker may be used with the same quantity of brown rice and water.
Heat canola oil in a small skillet. Add onions, celery, and garlic. Cook over medium heat for 5 minutes or until tender. Remove from heat. Cover and refrigerate until completely cooled.
In a medium mixing bowl, combine turkey, egg, cranberries, spinach, Worcestershire sauce, salt, peppers, brown rice, and sautéed vegetables. Mix well. Shape into 6 patties.
Line a large baking sheet with parchment paper and lightly coat with nonstick cooking spray. Place patties evenly spaced on baking sheet.
Bake uncovered for 20-25 minutes at 350 °F to an internal temperature of 165 °F or higher for at least 15 seconds (use a food thermometer to check the internal temperature). Do not overcook. Remove from oven and serve on a mini whole-wheat roll. Serve immediately.
May be served with onion, lettuce, tomatoes, ketchup, and mustard.