Place the chicken thighs in a large bowl or zip top bag. Set aside.
In a small bowl, whisk together the pesto, olive oil, lemon zest and juice. Season with salt and pepper.
Pour the marinade over the chicken and allow to sit for 1 hour or overnight.
Preheat the grill on high.
Remove the chicken from the marinade and discard the remaining marinade.
Place the chicken on the grill skin side down and cook for 4-5 minutes. If the fat rendering from the chicken causes flare ups, turn the heat to low.
When the skin is crisp, flip the chicken over and continue cooking for an additional 4-5 minutes.
Turn the heat to low (if you have already done so) and close the lid.
Continue to grill the chicken for an additional 4-5 minutes on each side or until the chicken registers 185˚F on an instant read thermometer when inserted into the thickest part of the thigh.)
Transfer the chicken to a platter and rest for 5-10 minutes.
Serve with chopped Basil, if desired.
Notes
Chicken Thighs can be marinated for up to 8 hours in the refrigerator.