In a medium bowl, toss chopped apples with lemon juice to prevent browning.
Add grapes, celery, and walnuts to the bowl and toss to combine.
In a small bowl, whisk together the mayonnaise, Greek yogurt, honey, salt, and pepper.
Pour the dressing over the apple mixture and stir until evenly coated.
Serve on a bed of butter lettuce or mixed greens. Enjoy chilled or immediately.