Preheat oven to 350 degrees F. Line a 13- x 9-inch baking dish with heavy duty foil and coat the foil with non-stick cooking spray. If you prefer not to use foil, generously coat the baking dish with non-stick cooking spray.
Add the olive oil to a medium skillet and place it over MEDIUM-LOW heat. When hot, add the onions. Season with 1/2 teaspoon salt and pepper and sauté for 5 to 6 minutes, or until translucent, but not browned. Add the mushrooms and sauté for 2 to 3 minutes, or until they release their liquid. Remove from heat and allow to cool.
Meanwhile, add the eggs to a large mixing bowl and whisk lightly. Add the ground turkey, bread crumbs, BBQ sauce, Worcestershire sauce, thyme, smoked paprika, granulated garlic or garlic powder, remaining salt, and the onion and mushroom mixture. Mix until all the ingredients are well incorporated but avoid overworking the mixture. Pour the meatloaf mixture out into the prepared baking dish and shape into an oval, football shaped loaf. Bake for 30 minutes.
Meanwhile, combine the sauce ingredients in a small bowl. After the initial baking time, remove the meatloaf from the oven and pour the sauce over the top. Use the back of a spoon to spread it out over the top to the edges of the meatloaf. Return the meatloaf to the oven and continue to bake for an additional 25 to 30 minutes, or until the internal temperature is 165 degrees F when checked with an instant read thermometer. Remove from the oven and allow to rest for 5 to 10 minutes before slicing.
Serve hot, at room temperature, or cold in a sandwich.