1. Cook beans in boiling water to cover in a large saucepan over medium-high heat 4 minutes or until crisp-tender; drain. Plunge into ice water to stop the cooking process; drain.
2. Whisk together Worcestershire sauce and next 4 ingredients in a small bowl. Pour marinade into a large zip-top plastic freezer bag; add beans and onion. Seal bag, and shake to coat. Chill 3 hours, turning occasionally. Serve with a slotted spoon. Garnish, if desired.