BRING 1-1/2 qt. (6 cups) salted water to boil in large saucepan on medium-high heat. Add barley; return water to boil. Reduce heat to medium-low; simmer 45 min. or until barley is tender. Drain; cool. Cover and refrigerate up to 4 days.
BEAT dressing mix, lemon juice, vinegar and oil in large bowl with wire whisk until well blended. Add barley; toss to coat.
CUT asparagus into 1-inch lengths. Add to barley mixture along with the peas and lemon peel; mix lightly.