Preheat oven to 400°F.
Slice zucchini in half lengthwise, leaving the peels on. Dice tomato and onion, and mince garlic.
Scoop out the centers of the zucchini, leaving at least 1/4 inch around the edges and bottoms; save the centers in a bowl.
Dice 1/2 cup zucchini from the reserved centers, and set aside; this will go in the filling.
Drizzle the zucchini shells with 1/2 tablespoon of olive oil, using your hands to rub it over all sides. Sprinkle with salt and pepper to taste, then set aside.
In a large skillet over medium heat, cook turkey until no longer pink; stir frequently to crumble.
Drain any excess grease if necessary, then add onions, garlic, and the 1/2 cup zucchini to the skillet. Cook for 2-3 minutes until onion is tender, then add the tomato, basil, and a bit more salt and pepper if desired. Remove pan from heat and set aside.
Place the zucchini shells on a baking sheet, flesh side up; bake for 10-15 minutes or until slightly tender.
Meanwhile, add cheese and bread crumbs to the filling mixture and stir to combine.
Remove zucchini shells from the oven and fill evenly with the veggie mixture. Top each zucchini with an additional sprinkling of cheese and bread crumbs, then drizzle the remaining oil over top.
Return to the oven and cook for another 5-7 minutes or until completely softened.
Serve with grapes on the side.