At the James Reserve, there is parking for approximately 20 vehicles. If you plan on bringing bigger groups to the James, please carpool. The parking lot is just below the main building, Trailfinders Lodge, where visitors have to go to register. A map of the buildings at the James can be found here.
At the Oasis de los Osos Reserve, there is a small parking area near the gate leading to the area. There is room for at least 4-5 vehicles.