Cut the tops off the bell peppers and remove the seeds and membranes.
In a medium saucepan, bring the vegetable broth to a boil. Add the couscous, cover and reduce heat to low. Cook for 10 minutes or until all of the liquid is absorbed.
Meanwhile, heat the olive oil in a large skillet over medium heat. Add the onion, celery, carrots and garlic. Cook for 5 minutes or until vegetables are tender.
Stir in Italian seasoning and season with salt and pepper to taste.
Add cooked vegetables to cooked couscous and mix until combined.
Fill each bell pepper with couscous mixture. Place in a baking dish filled with 1 inch of water.
Bake for 25-30 minutes or until peppers are tender.