Bring 1 cup of water to a boil in a medium saucepan; gradually stir in couscous. Remove from heat; cover and let stand 5 minutes. Fluff with a fork.
While couscous stands, sprinkle lamb with salt and 1/8 teaspoon pepper. Place lamb on a broiler pan coated with cooking spray; broil 5 minutes on each side or until desired degree of doneness.
While lamb cooks, combine 1/8 teaspoon pepper, yogurt, and remaining ingredients. Serve lamb over couscous with yogurt sauce.