In small bowl, combine all dressing ingredients; mix well. Set aside.
In medium saucepan, bring water to a boil. Add barley; return to a boil. Reduce heat to medium-low; cover and simmer 10 to 12 minutes or until barley is tender and only about 1/4 of liquid remains.
Add chicken and garlic; mix well. Cover; cook an additional 5 minutes. Stir in vegetables. Cover; cook over medium heat until chicken is no longer pink and vegetables are tender. Add dressing; cook until thoroughly heated.
Arrange spinach leaves on 2 individual plates. Spoon salad onto spinach leaves.