1. Marinate the Chicken: In a large bowl, whisk together lime juice, cilantro, garlic, olive oil, salt, and pepper. Add chicken breasts and coat well. Cover and refrigerate for at least 30 minutes.
2. Preheat: If grilling, preheat grill to medium-high (375°F). For baking, preheat oven to 400°F.
3. Prepare to Cook: Remove chicken from marinade and let excess drip off. Lightly oil grill grates or spray a baking dish with nonstick spray.
4. Grill or Bake: Grill each side for about 6 minutes until cooked through (internal temp of 165°F) or bake for 25-30 minutes until golden brown.
5. Serve: Let rest for 5 minutes before slicing. Drizzle with remaining marinade sauce if desired.