Cook the pearl couscous according to the package directions. Set aside in a large bowl.
In a small skillet, heat 2 tablespoons of the oil over low heat. Add the onion and cook until caramelized, about 20 minutes.
Meanwhile, preheat the broiler.
On a sheet pan, toss the zucchini with the remaining 2 tablespoons of oil and a pinch each of salt and pepper. Slide under the broiler and broil until cooked through and charred slightly, about 5 minutes.
Add the zucchini and onion to the cooked couscous. Add the lemon juice, parsley, vinegar, arugula, goat cheese, and some salt and pepper and toss to fully combine before serving.
