In a mixing bowl, whisk together the olive oil, soy sauce, orange juice, liquid smoke, Dijon mustard, garlic powder, and black pepper until smooth.
Poke the chicken breasts several times all over with a fork to help the marinade penetrate.
Place the chicken in a zip-top bag or shallow dish and pour the marinade over it, turning to coat so the chicken is fully covered.
Refrigerate the chicken for at least 30 minutes and up to 4 hours.
Heat the grill or grill pan to medium and brush the grates or surface with oil to prevent sticking.
Grill the chicken 4–6 minutes per side, depending on thickness, until an instant-read thermometer inserted into the thickest part reads 165°F (74°C).
Remove the chicken from the grill and let rest for 5 minutes before serving.