In a 6-qt. stockpot, heat oil over medium heat. Add carrots, onion and garlic; saute until carrots are tender, 4-5 minutes., Stir in orzo, chicken and broth; bring to a boil. Reduce heat; simmer, uncovered, 5 minutes. Stir in peas, spinach and dill; return to a boil. Reduce heat; simmer, uncovered, until orzo is tender, 3-4 minutes. Stir in lemon juice. If desired, top each serving with coarsely ground pepper.