In small microwavable bowl, microwave semisweet chocolate chunks and oil uncovered on High 30 to 60 seconds, stirring every 15 seconds, until melted; stir well. Spread chocolate glaze over brownies. If desired, place glaze in small plastic food-storage bag and cut off small tip from one corner of bag; drizzle glaze in diagonal lines over brownies. Let stand until glaze is set. For brownies, cut into 6 rows by 6 rows.