Preheat your oven to 375°F (190°C).
Prepare the bell peppers by cutting off the tops and removing the seeds and membranes.
In a large saucepan, bring the vegetable broth or water to a boil. Once boiling, stir in the couscous, remove from heat, cover, and let it sit for about 5 minutes, or until the couscous has absorbed the liquid.
In a medium skillet on medium heat, add 1 tablespoon of olive oil, mushrooms, zucchini, garlic, italian seasoning, salt and pepper. Stir until veggies are browned and cooked, about 3 to 5 minutes.
Add the cooked couscous and parmesan to veggie mixture and mix well to combine.
Stuff the prepared bell peppers with the couscous mixture, pressing the filling down gently to pack it in.
Place the stuffed peppers in a baking dish and drizzle olive oil over the tops of the peppers.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes or until the peppers are tender.
Remove the foil, top with more parmesan cheese and return dish back to oven for another 10-15 minutes of baking to allow the tops to brown slightly.
Once the stuffed peppers are cooked through, remove them from the oven and let them cool for a few minutes before serving.