Preheat your grill to medium heat, about 375 to 400 degrees F. Lightly oil the grates to prevent sticking.
Pat the fish fillets dry with paper towels. This helps you get those nice grill marks like in the photo.
In a small bowl, mix together the olive oil, lemon juice, lemon zest, thyme, parsley, garlic powder, salt, and black pepper.
Brush both sides of each fillet with the lemon herb mixture.
Place the fillets directly on the grill. Cook for 3 to 4 minutes per side, depending on thickness. The fish should be opaque and flake easily with a fork.
Remove from the grill and transfer to a serving platter. Garnish with fresh parsley and lemon slices.