In a large bowl cream together the butter, brown sugar and white sugar until light and fluffy. Add the eggs one at a time, mixing well with each addition. Stir in the vanilla, bananas and peanut butter.
Combine the flour, baking powder, bicarbonate of soda and salt; gradually stir into the creamed mixture.
Stir in the rolled oats and cooking chocolate. Drop by rounded spoonfuls onto an unprepared baking tray.
Bake for 8 to 10 minutes in the preheated oven. Allow biscuits to cool on baking tray for 5 minutes before removing to a wire rack to cool completely.