01 - In a medium bowl, whisk together the maple syrup, Dijon mustard, olive oil, apple cider vinegar, garlic, thyme, salt, and black pepper until well combined.
02 - Place chicken breasts in a large resealable bag or shallow dish. Pour the marinade over the chicken, ensuring all pieces are coated. Seal or cover and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor.
03 - Preheat your grill to medium-high heat. Lightly oil the grill grates.
04 - Remove chicken from the marinade, shaking off excess liquid. Discard the leftover used marinade.
05 - Grill chicken for 5–7 minutes per side, or until fully cooked and internal temperature reaches 165°F.
06 - Remove from grill and let rest for 5 minutes before slicing. Garnish with fresh parsley and serve with lemon wedges, if desired.