Spray a 9x12-inch pan with cooking spray and set aside.

Heat a large saucepan on low heat.

Melt the light butter spread, ensuring the bottom of the pot is coated to prevent sticking.

Add marshmallows and melt on low flame, stirring until completely melted.

Remove from heat and stir in Rice Krispies until well coated.

Press the mixture into the prepared pan with wax paper and allow to cool slightly.

Cut into 16 squares and serve.