Preheat the grill to medium-high heat. Brush the chicken breasts with olive oil and season with salt and pepper. Grill the chicken for about 6-7 minutes per side, or until fully cooked and internal temperature reaches 165°F. Remove from the grill and let rest for 5 minutes before slicing.
While the chicken is resting, prepare the dressing. In a small bowl, whisk together olive oil, apple cider vinegar, honey, Dijon mustard, salt, and pepper until well combined. Adjust seasoning to taste.
In a large salad bowl, combine the mixed greens, cherry tomatoes, avocado, hard-boiled eggs, crumbled bacon, and blue cheese if using.
Slice the grilled chicken and add it to the salad. Drizzle the honey Dijon dressing over the top and toss gently to combine.
Serve immediately, or chill in the refrigerator for up to 30 minutes before serving for a refreshing meal.