Cut off tough ends of asparagus. Steam in boiling water, covered, 5 minutes or until crisp-tender. Strain and run under cold water. Strain well.
Slice off white part of green onion. Lay onion tops in a bowl and pour boiling water overtop. Strain immediately and run under cold water.
Separate asparagus into 10 bunches, add 2 bell pepper strips to each bunch. Secure bunches with green onion strip.
Arrange bunches in a 13 by 9 inch baking dish.
Mix together chopped onion, vinegar, water, sugar, oregano, tarragon, mustard, Worcestershire, salt, and pepper in a bowl. Spoon mixture over asparagus. Wrap with plastic wrap and place in refrigerator for at least 2 hours.
When ready to serve, take bunches out of the marinade and place on a serving dish.