1. Heat oil in a large heavy skillet over medium heat.
2. Season ribs with salt and pepper.
3. Place ribs in skillet and brown on both sides.
4. Arrange the ribs in your crock pot.
5. Put the sliced onion on top of the ribs.
6. In separate bowl, mix together taco seasoning and water and pour over ribs.
7. Cook, covered, for 8 hours on LOW.