1. Heat the oil in a large skillet over medium-high heat.
2. Add the onion and cook for 3 minutes, until soft.
3. Add the cabbage and apples and cook for 3 to 5 minutes, until the cabbage starts to wilt, stirring frequently.
4. Add the vinegar and brown sugar and mix well.
5. Cover and cook for 8 to 10 minutes, until the cabbage and apples are very soft, stirring occasionally.
6. Season to taste with salt and freshly ground black pepper before serving.