Preheat the oven to 350 degrees F. Coat a cookie sheet with cooking spray.

Sift together flour and baking powder; set aside. With an electric mixer at high speed, cream margarines and brown sugar together well. Beat in the peanut butter and vanilla; blend well. Add the eggs, one at a time, beating well after each addition. Gradually add the flour mixture; mix until blended. Fold in the miniature M + M 's.

Spread the batter into the prepared pan. Bake for 18 to 20 minutes or until the edges begin to pull away from the sides of the pan. Cool thoroughly on a wire rack. Cut into bars. Drizzle melted chocolate over bars and refrigerate just until chocolate is set. Store in airtight container. Freezes well.

Adapted