Prep the Herb Sauce: In a small bowl, stir together the extra-virgin olive oil, chopped parsley, chopped mint, lemon zest, and lemon juice. Season generously with kosher salt and black pepper, stir well, and set aside so the flavors meld while you grill.
Prep the Grill and Skewers: Preheat your outdoor grill or indoor cast-iron grill pan to medium-high heat (around 400°F–450°F). If using wooden skewers, soak them in water for 30 minutes.
Thread the Vegetables: Thread the prepped vegetables onto the skewers in an even pattern. Place sturdy onion wedges and eggplant pieces on the outer ends, weaving shishito peppers, poblano squares, jalapeños, and cherry tomatoes securely through the middle.
Season Generously: Spray or brush all sides of the loaded skewers with extra-virgin olive oil, then season evenly with kosher salt and black pepper.
Grill to Char: Place kebabs on the hot grill grates. Cook for 10 to 12 minutes, turning every 2 to 3 minutes, until the vegetables are tender, the edges are slightly caramelized, and the tomatoes are blistered.
Serve: Slide the charred vegetables off the skewers directly onto a warm platter of fluffy cooked couscous. Spoon the fresh lemon-herb sauce generously over top and serve immediately.