Heat oil in large skillet over medium-high heat until hot. Add beef roast; cook about 10 minutes or until browned on all sides, turning occasionally. Sprinkle with salt and pepper.
Place onions in 3 1/2- to 6-quart slow cooker. Place beef on onions. In small bowl, combine all remaining ingredients; mix well. Pour over beef and onions.
Cover; cook on low setting for 8 to 10 hours.
With slotted spoon, remove beef and onions from slow cooker. Cut beef into slices. If desired, skim fat from beef juices in slow cooker. Serve beef with juices.