1) In a large bowl combine the lemon juice, parsley, chives, rosemary, garlic, olive oil, salt and pepper. Whisk until well combined. Add the chicken breasts and using clean hands, toss the chicken in the marinade until well coated. Cover and let sit in the fridge for 2-3 hours.
2) Meanwhile, make the corn salsa. In a medium bowl, combine the corn, red onion, lime juice, and salt. Carefully toss in the diced avocado and store in fridge until ready to use.
3) Preheat the grill to medium/high heat. Cook chicken for 6-7 minutes on each side, per 1 inch thickness. So if the chicken is about 1 inch thick, cook for 6-7 minutes per side. If chicken breasts are very thin, you may shorten cooking time to 4-5 minutes per side.
4) Once chicken is cooked, remove from grill and let rest for at least 10 minutes. Slice chicken and serve with the corn salsa. YUM!