Prepare the vegetables: Add the fingerling potatoes, carrots and green beans to the bottom of a 6-quart slow cooker. Drizzle with the olive oil and season lightly with salt and pepper. Toss to coat. Pour the chicken broth around the vegetables. The small amount of broth will create moisture as everything cooks and help prevent the bottom of the slow cooker from scorching.
Make the meatloaf: Add the ground turkey, breadcrumbs, ketchup, BBQ sauce, salt, black pepper, onion powder, garlic powder, smoked paprika, Italian seasoning, red onion, red bell pepper and green bell pepper to a large bowl. Using clean hands, gently mix just until the ingredients are evenly incorporated. Do not overmix, which can make the meatloaf dense.
Shape the meatloaf: Shape the turkey mixture into a compact loaf, about 7 inches long and 3 to 4 inches wide. Place the meatloaf directly on top of the vegetables in the center of the slow cooker. It is fine if some of the vegetables sit around the sides of the meatloaf.
Cook: Cover and cook on HIGH for 3 1/2 hours. Avoid repeatedly lifting the lid during cooking, as this releases heat from the slow cooker.
Make the glaze: About 30 minutes before the end of the cooking time, stir together the ketchup, BBQ sauce, brown sugar and Worcestershire sauce in a small bowl until smooth.
Glaze the meatloaf: Open the slow cooker and generously spoon or brush the glaze over the top and sides of the meatloaf. Cover and continue cooking on HIGH for about 30 minutes, or until an instant-read thermometer inserted into the thickest part of the meatloaf registers 165°F. The potatoes and carrots should be fork-tender and the green beans should be tender.
Rest and serve: Carefully transfer the meatloaf to a cutting board or serving platter and let it rest for 5 to 10 minutes before slicing. Taste the vegetables and season with additional salt and pepper, if needed. Serve the sliced turkey meatloaf with the fingerling potatoes, carrots and green beans alongside.