Peanut Butter Swirl Bars

1/2 cup peanut butter
1/3 cup softened margarine
3/4 cup firmly packed brown sugar
3/4 cup granulated sugar
2 eggs
2 tsp. vanilla
1 cup flour
1 tsp. baking powder
1/4 tsp. salt
1 (6 oz.) pkg. chocolate chips

Cream together peanut butter and margarine; gradually. Add sugars, beating well at medium speed of an electric mixer. Add eggs and vanilla and beat well. Combine flour, baking powder and salt in a small bowl; stir well. Add flour mixture to creamed mixture, mixing well. Spread batter in a greased 9x13x2 inch pan and bake at 350 degrees for 5 minutes. Remove from oven and sprinkle with chocolate chips. Swirl through batter with a knife. Return to oven and bake 20 minutes or until edges start to pull away from the pan. Do not over bake. Let cool and cut into bars.