Cook ancient grains according to package directions, using vegetable broth. (Do not lift lid or stir while cooking.)
Meanwhile, halve peppers lengthwise through stems; remove seeds and ribs. Boil peppers in a large pot of boiling water for 5 minutes or until tender; drain on paper towel. Set aside; keep warm.
Heat oil in a large non-stick skillet over medium heat. Add onion; cook, stirring, for 6 minutes, until soft. Stir in garlic, cook for 1 minute. Stir in ground round, roasted peppers and pizza sauce. Cook for about 3 minutes, stirring occasionally, until heated through.
Stir in ancient grains, tomato and parsley.
Place prepared pepper halves in large baking dish. Fill each with ground round mixture, mounding high. Top with cheese. If desired, place under broiler to melt cheese.