Begin by washing and patting dry your zucchini, red bell pepper, red onion, and portobello mushrooms. Slice them into uniform ½-inch thick pieces to ensure even grilling.

In a large mixing bowl, toss the sliced vegetables with half of your olive oil and balsamic vinegar mixture. Let them sit for about 5 minutes to absorb the flavors.

In a separate bowl, combine the remaining olive oil, balsamic vinegar, honey (or maple syrup), minced garlic, sea salt, and black pepper.

Preheat your grill or grill pan to medium-high heat, approximately 400°F.

Carefully place the marinated vegetables on the preheated grill. Grill each side for about 3–4 minutes until they become tender.

Cut your ciabatta rolls in half and place them cut-side down on the grill for 1-2 minutes until lightly charred.

Once the bread is toasted, layer the grilled veggies evenly on the bottom half of each roll. Top with slices of fresh mozzarella and drizzle generously with the reserved balsamic glaze.

If desired, place the assembled sandwich back on the grill for an additional minute to slightly melt the mozzarella.