Brush both sides of the watermelon slice with 1 tablespoon olive oil. Season with salt and pepper. Place the watermelon slice, cut side down on the grill grates and cook for 2 to 3 minutes. Flip the slice over and grill for an additional 2 minutes.
Transfer the watermelon to a platter and cut into 6 wedges. Top with the arugula, blueberries, tomatoes and parmesan. Drizzle with the remaining olive oil. Serve immediately.