Bring a large pot of water to a boil. Carefully separate 8 large leaves from the cabbage and blanch them for 2 minutes until pliable. Drain and set aside to cool.
Heat the olive oil in a skillet over medium heat. Add the onion and garlic and cook for 3 minutes until softened.
In a mixing bowl, combine the ground turkey, cooked wild rice, cooked onion and garlic, oregano, salt, and pepper. Mix until evenly blended.
Lay each cabbage leaf flat and place about 1/3 cup of filling near the stem end. Fold in the sides and roll tightly to enclose the filling.
Spread 1/2 cup tomato sauce across the bottom of a baking dish. Arrange the rolls seam side down in the dish. Pour the remaining tomato sauce over the top.
Cover the dish with foil and bake at 375°F for 35 minutes until the turkey is cooked through and the rolls are tender.