Cut peppers in half lengthwise; remove stems and seeds. Set aside. In a large bowl, combine egg, onion, bread crumbs, garlic powder, herbs, onion powder, salt and pepper. Crumble beef over mixture and mix well. Spoon into pepper halves; brush with oil.
Prepare grill for indirect heat, using a drip pan. Place peppers over drip pan. Grill, covered, over indirect medium heat until beef is no longer pink and peppers are tender, 30-35 minutes. Serve with marinara sauce.