In a large bowl, beat butter and brown sugar until light and fluffy. Beat in egg, salt, bananas and peanut butter. Stir in the rolled oats. Mix well. Spread in a greased 13 X 9 X 5 cm pan. Bake in a 180ºC . oven for 1 hour or until a wooden pick inserted in the center comes out clean. Cut into 2 x 3 cm bars. Makes about 4 dozen bars.