Wash the zucchinis thoroughly.
Cut the zucchinis in half lengthwise.
Mix olive oil, garlic powder, salt, black pepper, and Italian seasoning in a bowl.
Brush the zucchini halves with the olive oil mixture on both sides.
Preheat the grill to medium-high heat.
Place the zucchinis cut-side down on the grill.
Grill for about 5-7 minutes until grill marks appear.
Flip the zucchinis and grill for another 5-7 minutes.
Remove the zucchinis from the grill and let them cool slightly.
Garnish with fresh basil leaves before serving.