1. Combine first 4 ingredients, 2 tsp. lemon zest, and 1/2 tsp. rosemary in a medium bowl. Shape into 30 (1-inch) meatballs (about 1 level tablespoonful each).
2. Sauté meatballs, in 2 batches, in 1 Tbsp. hot oil per batch in a Dutch oven over medium heat 3 to 4 minutes or until browned. Remove using a slotted spoon.
3. Sauté onion and next 2 ingredients in remaining 1 Tbsp. hot oil in Dutch oven over medium-high heat 3 to 5 minutes or until tender. Stir in broth, lemon juice, and remaining 2 tsp. zest and 1/2 tsp. rosemary. Bring to a boil, stirring occasionally. Add orzo. Reduce heat to medium; simmer, stirring occasionally, 7 to 9 minutes or until pasta is almost tender.
4. Stir in meatballs; simmer, stirring occasionally, 5 to 7 minutes or until meatballs are thoroughly cooked. Add salt and pepper to taste. Top with cheese and parsley.