In a small bowl, whisk together the cilantro, lime juice, olive oil, garlic, cumin, salt, and pepper.
Place the chicken breasts in a large ziplock bag or shallow dish, and pour the marinade over the chicken. Make sure the chicken is evenly coated in the marinade.
Marinate the chicken in the fridge for at least 30 minutes, or up to 4 hours.
Preheat the grill, oven, or skillet to medium-high heat.
Remove the chicken from the marinade and discard the remaining marinade.