In a large skillet, heat oil over medium heat. Add onion and reduce heat to low. Allow onion to caramelize, stirring only enough to prevent sticking and to be sure that all sides are fully cooked. Add garlic and saute briefly.
Increase heat to medium. Add chicken hindquarters to skillet and brown on both sides. Remove chicken, onion and garlic and place in a 9x13 inch baking dish.
Combine the stock and vinegar. Deglaze the skillet with this mixture, then bring to a boil and continue to simmer, stirring occasionally, until the mixture has thickened. Pour mixture over chicken and stir in the sun dried tomatoes. Cover dish tightly and bake in the preheated oven for 15 to 20 minutes, or until chicken is done and juices run clear.