Cream the butter, peanut butter and sugar together until light and fluffy.
Beat in the orange zest, followed by the egg.
Sift in the flour and bicarbonate of soda and add the oats. Mix until just combined.
Place heaped teaspoonfuls well apart on a large lined baking tray or two small ones.
Place in a ready heated oven and bake at 180℃ (350℉, Gas 4) for 10-12 minutes, depending on how well done you like your biscuits.
Once out of the oven, leave on the baking tray for a minute or two to firm up, then transfer to a wire rack to cool.
Add 75g of chocolate chips for an extra chocolatey dimension.Please note: calories and other nutritional information are per serving. They're approximate and will depend on serving size and exact ingredients used.