Preheat the oven to 375°F (190°C).
Cut the tops off the bell peppers and remove the seeds and membranes. Rinse them well.
In a medium saucepan, combine the quinoa and vegetable or chicken broth.
Bring to a boil, then reduce heat to a simmer, cover, and cook for about 15 minutes or until the quinoa is cooked and the liquid is absorbed.
Fluff with a fork and set aside.
In a large skillet, heat the olive oil over medium heat.
Add the chopped onion and cook until translucent.
Add the minced garlic, diced zucchini, and diced carrot.
Cook for about 5-7 minutes until the vegetables are softened.
Stir in the drained diced tomatoes, dried oregano, dried basil, salt, and pepper. Cook for an additional 2 minutes.
Remove the skillet from heat and combine the cooked quinoa with the vegetable mixture. Mix well.
Stuff the bell peppers with the quinoa-vegetable mixture, pressing down gently to pack the filling.
Place the stuffed peppers in a baking dish.
If the peppers don't stand up on their own, you can slice a small portion off the bottom to create a flat base.
Sprinkle grated cheese over the tops of the stuffed peppers.
Cover the baking dish with aluminum foil and bake in the preheated oven for about 25-30 minutes, or until the peppers are tender.
Remove the foil and bake for an additional 5-10 minutes, or until the cheese is melted and slightly golden.
Remove from the oven and let cool for a few minutes before serving.
Garnish with fresh parsley or basil leaves before serving.