Preheat oven to 350 degrees. Combine quinoa and chicken stock in a saucepan. Bring to a boil and reduce heat to simmer for 15-17 minutes until all of the liquid is absorbed. Meanwhile, cut the tops off of the bell peppers, remove the seeds and set aside in a baking dish sprayed with cooking spray. Chop the tops of the peppers (will add to the meat mixture later). Heat the olive oil over medium high heat in a large sauce pan and saute the garlic. Add chopped onions and peppers. Saute 2-3 minutes. Add the ground turkey, worcestershire sauce, salt and pepper to the pan. Cook until the meat is browned. Add the tomatoes and tomato paste. Stir to combine. Cook until most of the liquid is absorbed (5 minutes). Add the cooked quinoa to the meat mixture. Stir thoroughly. Fill each pepper with the mixture. Cook in preheated oven for 30 minutes. After 25 minutes, top each pepper with italian cheese. Cook five more minutes (cheese will melt and begin to brown). Serve immediately :) Enjoy!