Bring 1 1/2 cups water to a boil in a medium saucepan. Add barley; cover, reduce heat, and simmer 13 minutes. Remove from heat; let stand, covered, 5 minutes.
Combine parsley and cilantro in a food processor; process until minced. Add pine nuts; process until minced. Add cheese and next 5 ingredients (cheese through pepper); process until well-blended.
Spoon the barley into a bowl. Stir in the pesto, zucchini, tomato, and onion.