In lg bowl, combine beef strips, orange juice, vinegar, soy sauce, hot chili paste, brown sugar and garlic, stir to coat. Refrigerate 1 hr to marinate.
Strain beef in colander over lg bowl. Reserve marinade. Stir water and cornstarch into marinade. Whisk until cornstarch is dissolved.
Spray a wok or lg skillet w/cooking spray. Place over high heat. Cook beef, stirring for 1 min. Cook 1 min more. Stir in white parts of green onions and orange zest. Cook, stirring for 1 min. Stir in marinade and green parts of green onions. Cook, stirring until beef is no longer pink. Season w/ salt and pepper. Serve over rice or noodles.