In a deep skillet or Dutch oven, bring the chicken broth to a boil. Lower the heat and bring to a simmer.
Meanwhile, in a large bowl, combine the lamb, half of the parsley, the breadcrumbs, feta, egg, garlic and oregano; season with salt and pepper. Form into 1-inch balls. Add to the simmering broth along with the orzo and cook for 8 minutes. Stir in the lemon peel, lemon juice, remaining parsley and the mint.