In 12-inch skillet, heat oil over medium-high heat. Add onions and garlic; cook 4 to 5 minutes, stirring frequently, until onions are softened.
Stir in chili powder, cumin, salt, pepper and beef. Cook 6 to 8 minutes, stirring occasionally, until beef is lightly browned.
In 3- to 4-quart slow cooker, place beef mixture. Stir in beans, tomatoes and water.
Cover; cook on Low heat setting 8 to 10 hours. Stir well before serving.