Cut steak crosswise into thin slices, then cut each slice into thin strips. Place meat in medium bowl. Add garlic and crushed pepper; mix lightly. Combine next 4 ingredients.
Heat oil in large skillet on medium-high heat. Add meat, in batches; stir-fry 1 to 2 min. or just until meat strips are no longer pink in centers. Transfer to plate; set aside.
Add carrots and celery to skillet; stir-fry 2 min. Return meat to skillet along with the dressing mixture; stir-fry 1 to 2 min. or until meat is done and sauce is slightly thickened. Stir in onions.