Place zucchini, onions, and red bell pepper into a food processor, and pulse several times until finely chopped but not liquefied. Place the vegetables into a bowl, and mix in ground turkey, couscous, egg, Worcestershire sauce, and Dijon mustard until thoroughly combined. Fill each prepared muffin cup about 3/4 full. Top each cup with about 1 teaspoon of barbecue sauce. Bake in the preheated oven until juices run clear, about 25 minutes. Internal temperature of a muffin measured by an instant-read meat thermometer should be at least 160 degrees F (70 degrees C). Let stand 5 minutes before serving.