Heat large nonstick skillet over medium heat until hot.
Add ground beef, mushrooms, onion, carrot, and garlic; cook 8–10 minutes, breaking into 3/4-inch crumbles and stirring occasionally.
Pour off drippings.
Stir in broth, barley, salt, and pepper. Bring to a boil; reduce heat to medium-low.
Cover tightly and simmer for 10 minutes.
Add peas; continue cooking 2–5 minutes or until barley is tender. Stir in parsley and lemon peel.
Cook’s Tip’: Cooking times are for fresh or thoroughly thawed ground beef. Ground beef should be cooked to an internal temperature of 160 degrees. Color is not a reliable indicator of ground beef doneness.