Soak around 8 wooden skewers in water for 15-30 minutes to prevent burning. Mix together the balsamic vinegar, olive oil, lemon juice, mustard, garlic cloves, fresh herbs, salt, and pepper. Toss with the chopped vegetables. Let sit for 15 minutes for the vegetables to soak up some of the flavors from the marinade.
Grill for 6-8 minutes and then flip and continue to cook for 4-6 minutes until vegetables are lightly charred and cooked through. For more char, turn the vegetables every 3-4 minutes to cook on all four sides.