Preheat oven to 350 degrees F. Place ground beef in a large bowl; set aside. In a small nonstick skillet heat the 1 teaspoon oil over medium heat. Add carrot, sweet pepper, and onion; cook until tender. Cool carrot mixture slightly. Add to bowl with beef. Add oats, walnuts, egg, egg white, salt, mustard, and black pepper; mix well. Pat meat mixture into an 8x4x2-inch loaf pan. Bake for 1 to 1 1/4 hours or until an instant-read thermometer inserted in center registers 160 degrees F. Remove from oven and let meat loaf stand for 5 minutes. Using two spatulas, transfer loaf to a serving platter. Top with Gremolata.
Meanwhile, for vegetables, in large bowl toss Brussels sprouts and sweet potatoes with the 1 tablespoon oil to coat. Place vegetables in a 15x10x1-inch baking pan. Bake vegetables with the meat loaf for the last 30 to 40 minutes of baking time or until vegetables are tender. Increase oven temperature to broil.
Arrange bread slices on a baking sheet. Broil 6 inches from the heat for 1 to 2 minutes or until toasted. Remove from oven; sprinkle with cheese. Broil about 1 minute more or until cheese is melted.
For relish, gently toss together sliced apples, chopped cranberries, and chopped orange. Drizzle with honey.
In a small bowl combine 1/4 cup snipped fresh parsley; 1 tablespoon finely shredded lemon peel; and 2 cloves garlic, minced.