Heat oil in a large nonstick skillet over medium-high heat. Sprinkle turkey with 1/8 teaspoon salt and 1/8 teaspoon pepper. Add turkey to pan; cook 2 minutes on each side or until done. Divide turkey between 2 plates; keep warm.
Add onion to pan. Cook 3 minutes, stirring frequently; add remaining 1/4 teaspoon salt and remaining 1/8 teaspoon pepper. Cook 5 minutes or until onion is tender and golden, stirring frequently. Stir in water, cranberries, and vinegar; cook 2 minutes or until cranberries are tender. Remove from heat; stir in parsley, if desired.