TOSS meat with cornstarch. Mix dressing and zest in separate bowl.
HEAT 2 Tbsp. dressing mixture in skillet on medium-high heat. Add meat; cook 3 min.
ADD bok choy and remaining dressing mixture; cook and gently stir 2 min. or until bok choy and meat are coated and heated through.
serving size = 1-1/4 cups (300 mL)