Heat oil in large nonstick skillet over med. heat. Add oregano, garlic powder, lemon peel and pepper. Cook and stir just until fragrant. Add chicken. Cook and stir 4 minutes. Stir in broth, orzo, olives and garlic. Bring to a boil over high heat. Reduce heat; simmer, partially covered, 15 min. or until pasta is tender and chicken is cooked through, stirring occasionally.
Stir in spinach and feta. Cover; let stand 2 to 3 min. or until spinach wilts. Top with additional feta, if desired.