Heat olive oil in a large skillet over medium heat. Add green tomato, zucchini, and onion; cook and stir until zucchini starts to brown, about 5 minutes. Add couscous and garlic; cook and stir until couscous is lightly toasted, about 3 minutes.
Stir chicken stock, salt, and pepper into the skillet. Simmer, covered, until couscous is tender, 8 to 10 minutes. Serve garnished with lemon wedge and chopped parsley.
