Preheat the pellet smoker to 275°F. Set it up for indirect cooking and use a mild wood such as apple or cherry.
In a large bowl, whisk the egg with the milk. Stir in the breadcrumbs, roasted red peppers, grated onion, garlic, 1 tablespoon parsley, thyme, salt, and black pepper. Add the ground chicken and mix gently until just combined.
Shape the mixture into a compact loaf on a piece of foil or a small rimmed pan. Brush the top and sides with olive oil. Place the loaf in the smoker and cook until the center reaches 165°F, checking with an instant-read thermometer.
While the meatloaf cooks, bring the chicken broth to a boil in a small saucepan. Stir in the couscous, cover the pan, and remove it from the heat. Let it stand for 5 minutes, then fluff with a fork. Fold in the dill, lemon juice, and remaining parsley.
Rest the smoked meatloaf for 5 minutes before slicing. Serve the slices over the herb couscous.