Wash the banana peppers under cold water, cut off the tops, and remove the seeds.
Cook the orzo pasta in salted boiling water until al dente, about 8-10 minutes, then drain.
In a large pot, heat olive oil over medium heat, sauté diced onion for 5 minutes, then add minced garlic and cook for 1 minute.
Add diced tomatoes, vegetable broth, oregano, basil, salt, and pepper to the pot and bring to a gentle simmer.
Mix the cooked orzo with the soup base and stuff the banana peppers with the mixture.
Pour any remaining soup mixture around the stuffed peppers in a baking dish and ensure they stand upright.
Cover the baking dish with aluminum foil and bake for 25 minutes, then remove the foil, add mozzarella cheese, and bake for an additional 10 minutes.