1Heat oven to 375°F. Spray 15x10x1-inch pan with cooking spray.
2In large bowl, beat butter, sugar and vanilla with electric mixer on medium speed until fluffy. Add pumpkin, flour and pumpkin pie spice; beat until blended. Stir in chocolate chips. Press dough in pan with greased hands.
3Bake 18 to 20 minutes or until golden brown. Cool completely in pan on cooling rack, about 1 hour.
4In small microwavable bowl, microwave frosting uncovered on High 15 to 30 seconds, stirring once, until melted and smooth. With fork, drizzle frosting over bars. Let stand until set, about 10 minutes. Cut into 6 rows by 4 rows.