Preheat your grill and oil the grates.
Use 1/2 teaspoon of olive oil and salt and pepper to season the fillets on both sides.
Coat the asparagus with 2 teaspoons of olive oil, and season with garlic powder, salt and pepper.
Set up the grill for direct cooking and place asparagus directly on the grill over medium heat, let it cook for 4 - 5 minutes.
After asparagus has been cooked for 4 - 5 minutes, turn the asparagus to cook the other side. Place the opah fillets on the other side of the grill over medium high heat. Let the fillets cook for 2 - 3 minutes.
After the opah has been cooked for 2 - 3 minutes or until it releases itself easily from the grill, flip and cook the other side for another 2 minutes.
Remove both opah and asparagus from the grill, drizzle the lemon sauce all over and enjoy.