Heat oil in a large skillet over medium heat. Cook and stir onion and garlic until slightly softened, about 3 minutes. Add jackfruit; cook and stir until lightly browned and relatively free of moisture, about 10 minutes.
Transfer jackfruit mixture to a slow cooker; cover with barbeque sauce. Cook on Low, stirring occasionally, until jackfruit shreds easily with a fork, about 6 hours.
