01 - In a medium bowl, whisk together the fresh orange juice, orange zest, Dijon mustard, olive oil, honey, minced garlic, thyme, salt, and black pepper until smooth and well combined.
02 - Place the chicken breasts in a large resealable plastic bag or a shallow dish. Pour the marinade over the chicken, ensuring all pieces are evenly coated. Seal tightly and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor penetration.
03 - Preheat your grill to medium-high heat. Lightly oil the grill grates to prevent sticking.
04 - Remove the chicken from the marinade, shaking off any excess. Discard the remaining used marinade. Place the chicken on the grill and cook for 6 to 7 minutes per side, until the internal temperature reaches 165°F (74°C) and the juices run clear.
05 - Transfer the chicken to a cutting board and let it rest for 5 minutes before slicing. Garnish with fresh orange slices and chopped parsley. Serve immediately.