Finely shred portion of peel of one orange to make 1/2 teaspoon peel; set aside. Halve orange; squeeze juice. Working over a bowl to catch the juice, peel and section the remaining oranges; set aside. Combine the juices to get 1/3 cup (add water, if necessary).
Rinse Brussels sprouts. Halve any large sprouts. In a medium saucepan cook sprouts, uncovered, in a small amount of boiling water for 10 to 12 minutes or until tender. Drain and transfer to a serving bowl. Gently stir in orange sections; cover and keep warm.
In the same saucepan melt margarine. Stir in cornstarch and thyme or five spice powder. Stir in reserved orange peel, orange juice, and mustard. Cook and stir until thickened and bubbly. Cook and stir for 1 minute more. Transfer Brussels sprouts and fruit to serving bowl. Top with sauce; toss to serve.