1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Stir together butter and sugar in large bowl. Add eggs and vanilla; beat with spoon or whisk until well blended. Combine flour, cocoa, baking powder and salt; add to butter mixture, stirring until well blended. Reserve 1/2 cup peanut butter chips for glaze; stir remaining chips into batter. Spread batter in prepared pan.
3. Bake 30 to 35 minutes or until wooden pick inserted in center comes out clean. Cool completely in pan on wire rack. Prepare PEANUT BUTTER CHIP GLAZE; drizzle over brownies. Let stand until glaze is set. Cut into squares. About 32 brownies.
PEANUT BUTTER CHIP GLAZE:
1. Combine 1/2 cup REESE'S Peanut Butter Chips (reserved from brownies), 2 tablespoons butter or margarine and 2 tablespoons milk in small microwave-safe bowl.
2. Microwave at MEDIUM (50%) 45 seconds; stir until chips are melted and mixture is smooth. Gradually add 1/4 cup powdered sugar, beating with whisk until smooth. About 1/2 cup glaze.