Preheat oven to 400°.
Combine parsnip, cauliflower, bell pepper, 2 teaspoons olive oil, black pepper, and salt on a jelly-roll pan coated with cooking spray, and toss well to coat. Bake at 400° for 20 minutes or until lightly browned, stirring after 10 minutes.
Heat remaining 1 teaspoon olive oil in a large saucepan over medium-high heat. Add onion; sauté 4 minutes or until browned. Add 3 cups broth and barley; bring to a boil. Cover, reduce heat, and simmer 30 minutes or until liquid is absorbed and barley is al dente. Add the remaining 1 cup broth, 1/2 cup at a time, stirring constantly until each portion of broth is absorbed before adding the next. Stir in parsnip mixture and 1/3 cup cheese. Sprinkle with the remaining 1/3 cup cheese, pecans, and parsley.