Preheat the grill to medium-high heat. Season the chicken breasts with salt and pepper, then grill for about 6-7 minutes on each side or until fully cooked. Remove from grill and let rest before slicing.

In a mixing bowl, whisk together honey, Dijon mustard, olive oil, apple cider vinegar, minced garlic, salt, and pepper until well combined.

In a large bowl, combine mixed greens, cherry tomatoes, cucumber, red onion, and feta cheese. Top with sliced grilled chicken and drizzle with honey mustard dressing. Toss gently to combine.