Brush the fish with oil and season both sides of the fish with the salt and pepper. Place the fish on the grill, and grill for 3 to 4 minutes or until golden brown and slightly charred. Turn the fish over and continue grilling, for 3 to 4 minutes for medium doneness. Remove the fish from the grill and let rest 5 minutes.
Drizzle mojo over snapper and serve with grapefruit slices on the side.
Combine all of the ingredients in a blender and blend until smooth.