Preheat oven to 375 degrees F. In a saucepan, combine the celery, garlic, garlic powder, onion, Italian seasoning, and marjoram, and saute in the olive oil. Add the mushrooms, and cook until the liquid evaporates. In a mixing bowl, combine the barley, oats, sunflower seeds, pecans, sesame paste, and soy sauce with the saute mixture. Mix all of the ingredients thoroughly, and stuff into cleaned and seeded bell peppers. Bake 30 to 40 minutes until done. Top with freshly grated Parmesan cheese.