In small bowl, combine steak sauce, chili sauce, water and mustard; set aside.
In large heavy saucepan, over medium-high heat, brown steak in oil.
Add onions, stirring until lightly browned.
Stir in sauce mixture; heat to a boil.
Cover; reduce heat and simmer 1 1/2 hours or until steak is tender.
Remove steak; cut into julienne strips.
Return steak to pan; cook and stir until hot.
Spoon steak mixture onto roll bottoms; replace tops.