Combine all of the marinade ingredients in a large ziplock bag. Add the chicken breasts, seal and shake to coat. Refrigerate for at least 6 hours to overnight.
Lightly grease the grates of an outdoor grill. Heat the grill to medium-high heat. Grill chicken for about 5-6 minutes per side or until fully cooked (the internal temperature has reached 165 degrees F.). Remove from the grill. Let the chicken rest for a few minutes and then chop it into small pieces.
Serve on warmed corn tortillas with cilantro, red onion and a squeeze of lime juice.