Spray cooker with cooking spray. In a large skillet over medium-high heat, brown flank steak in oil. Place in cooker. You may need to cut it in half to fit. In skillet, place onion, green chiles, water, vinegar, chili powder, garlic powder, sugar, salt and peper. Bring to a boil over medium heat, stirring to loosen browned bits from bottom of skillet. Pour over meat. Cover and cook until meat is very tender, 6 to 7 hours on low or 3 to 3 1/2 hours on high. Transfer meat to a warm platter. Slice meat diagonally. Remove onion from slow cooker with slotted spoon and arrange around meat. If desired, baste with juices.

From "The Austin American Statesman" typed by jessann :)