In a medium bowl, whisk together the orange juice, lime juice, olive oil, achiote paste, minced garlic, coriander, cumin, salt, smoked paprika, oregano, onion powder, and black pepper until well combined.
Place the chicken thighs in a large resealable plastic bag or shallow dish. Pour the marinade over the chicken and turn to coat evenly.
Refrigerate for 3–4 hours or overnight for the best flavor.
Preheat the grill to medium-high heat. Brush the grill grates with the olive oil to help prevent sticking.
Remove the chicken from the marinade and discard the remaining marinade.
Place the chicken on the grill and reduce the heat to medium. Grill for 5–8 minutes per side, or until the chicken reaches an internal temperature of 165°F.
Transfer the chicken to a plate and let it rest for 5 minutes before serving.
Notes
An instant read meat thermometer is the best way to know when the chicken is ready to enjoy. Ensure that the chicken has reached an internal temperature of 165 degrees F at the thickest part of the chicken thigh.