Preheat your grill to medium heat and allow it to fully warm up.
In a small bowl, whisk together the orange marmalade, Dijon mustard, lemon juice, white grape juice, salt, pepper, basil, and red pepper flakes until smooth.
Place the halibut on the grill skin-side down.
Spoon half of the glaze over the fish.
Close the grill lid and cook for about 10 minutes without moving the fish.
Check for doneness. The Orange Dijon Grilled Halibut is ready when it reaches an internal temperature of 145°F (63°C) and flakes easily with a fork.
Brush the remaining glaze over the fish during the last minute of cooking.
Remove from the grill and serve immediately.