1. Arrange beans in a steamer basket over boiling water. Cover and steam 15 minutes; set aside. Place onions in boiling water 3 minutes; drain.
2. Melt margarine in a large heavy skillet over medium heat; add sugar, and cook, stirring constantly, until bubbly. Add onions; cook 3 minutes, stirring constantly. Add beans; cook, stirring constantly, until heated.