1. Heat oil in a large nonstick skillet over medium-high heat. Add chicken and saute until cooked through (165 degrees F on an instant read thermometer), about 5 to 7 minutes, turning once. When cooked, transfer to a cutting surface and cut into 1/2-inch cubes. Spread out to cool to room temperature.
2. While chicken cooks, prepare the dressing. In a large bowl, whisk together Greek yogurt, mayo, lemon juice, mustard, garlic powder, and pepper.
3. Add cooled chicken, celery, grapes, cucumber, tomatoes, and onion to the dressing. Lightly toss to mix, until dressing coats ingredients. Stir in chopped parsley. Serve immediately, or chill several hours.
4. To serve, place lettuce leaves on 6 plates if desired and top with a scoop of chicken salad. Garnish with parsley sprigs if desired.
Source: Hannaford fresh Magazine, July - August 2014