Stack beef steaks; cut lengthwise in half and then crosswise into 1-inch wide strips.
Combine marinade ingredients, pour half over beef. Cover and marinade in refrigerator 10 minutes. Reserve remaining marinade.
Meanwhile cook pasta according to package directions; keep warm. Remove beef from marinade; discard marinade.
Heat large nonstick wok or skillet over medium-high heat until hot. Add beef (half at a time) and stir-fry 1 to 2 minutes or until outside surface is no longer pink. (Do not overcook.) Remove from skillet with slotted spoon; keep warm.
In same wok, combine pasta, spinach, water chestnuts, green onions and reserved marinade; cook until spinach is wilted and mixture is heated through, stirring occasionally. Return beef to skillet; mix lightly.