Shredded Beef for Tacos

2 to 3lbs round roast, cut into large chunks
1lg. onion, chopped
3T. oil
2 serrano chilies, chopped
3 garlic cloves, minced
1tsp. salt
1c. water

Brown meat and onion in oil. Transfer to slow cooker. Add chilies, garlic, salt, and water. Cover and cook on high for 6-8 hours.

Pull meat apart with two forks until shredded. Serve with fresh tortillas, lettuce, tomatoes, cheese, and guacamole.