1Heat oven to 425°F. In large bowl, toss parsnips, carrots, onion, oil, salt and pepper. Arrange vegetables in single layer in ungreased 17x12-inch half-sheet pan.
2Bake uncovered 35 to 40 minutes, stirring once, until tender and lightly browned.
3In 1-quart saucepan, heat vinegar, honey and mustard to boiling; cook 6 to 8 minutes, stirring occasionally, until glaze is reduced to 1/3 cup. Remove from heat; drizzle glaze over vegetables.