In a small bowl, whisk together the vinegar, mustard and garlic, slowly add the olive oil and whisk until combined. Season with salt and pepper.
Drizzle veggies with a little olive oil and season with salt and pepper
Preheat the grill. Grill the vegetables until just cooked through.
Cut the veggies in smaller bite size peices if desired (I left mine whole because they look so pretty!) Pour 1/2 the marinade over the vegetables and let sit at room temperature for 15 minutes.
Heat the olive oil over medium-high heat, add the couscous and toast until lightly golden brown. Cover the couscous with the hot stock plus hot water and bring to a boil, cook until al dente and drain well. Place in a large serving bowl, add the grilled vegetables and herbs and toss with the remaining vinaigrette. Serve at room temperature.