In small bowl, microwave semisweet chocolate chips with 1/2 teaspoon oil uncovered on High 45 to 60 seconds, stirring every 15 seconds, until smooth. Repeat with white baking chips and remaining 1/2 teaspoon oil. Drizzle on bars. Refrigerate about 30 minutes or cool at room temperature until chocolate is set. For bars, cut into 6 rows by 4 rows.