Preheat oven to 350 degrees F. Melt margarine in 3-qt saucepan over medium heat (3-5 minutes). Remove from heat. Stir in brown sugar, eggs, and vanilla. Add flour, baking powder, and salt; mix well. Stir in chocolate chips and peanuts.
Spread mixture into ungreased 13x9 inch baking pan.
Bake for 20-25 minutes or until center is firm to the touch. DO NOT OVER BAKE. Cool completely. Cut into bars.