Preheat oven to 350 degrees F. In large bowl, combine 1/2 cup crunch style peanut butter, 1/3 cup softened, 3/4 cup firmly packed brown sugar and 3/4 cup granulated sugar., beat until creamy. Gradually beat in 2 eggs and 2 tsp vanilla extract.
In a small bowl, combine 1 cup flour, 1 tsp baking powder and 1/4 tsp salt; blend into peanut butter mixture. Spread into greased 13″x9″x2″ baking pan. Sprinkle 2 cups semi-sweet chocolate chips over surface. Place in 350 degree F oven for 5 minutes. Remove from oven; run knife through to marbelize.
Return to oven. Bake 30 minutes