• Make the dressing. In a bowl, combine pesto, olive oil, vinegar, and lemon juice; add salt and pepper to taste, and whisk until combined. Pour half of the dressing into a ziploc bag. Place the other half in the fridge.
• Marinate the chicken. Add the chicken breasts to the ziploc bag, seal it, and shake it all up until well combined. Place the chicken in the fridge for 30 minutes, or for up to 2 hours.
• Prepare to grill. When you're ready to cook your chicken, preheat the grill to 400ºF. Brush grill grates with olive oil.
• Grill the chicken. Remove the chicken breasts from the marinade and place them on the hot grill. Cook without touching until the chicken breasts start getting some grill marks, about 5 minutes. Turn the chicken breasts over, cover the grill, and let them finish cooking, about 7 more minutes, depending on the thickness of the chicken. Chicken is done when a meat thermometer registers 165ºF.
• Rest. Remove the chicken from the grill. Cover and let it rest for 5 minutes before slicing.

Assemble the Salad

• Start with lettuce. In the meantime, prepare the salad and transfer the chopped lettuce to a large salad bowl.
• Add antipasto. Next, top the lettuce with tomatoes, cheese, and pepperoncini.
• Add the chicken. Cut the chicken breasts into strips and add them to the salad.
• Dress the salad. Pour the remaining basil pesto dressing over the salad; toss to combine. Serve.