Lightly butter the roasting tin.
Combine the butter, syrup and sugar in a saucepan and heat gently until the ingredients has melted and dissolved. Stir in the oats and mix well.
Soon into the prepared tin and smooth the surface with a spoon or palette knife. Bake in a preheated oven at 180C/160C Fan/Gas Mark 4. for about 30 minutes.
Leave to cool in the tin for about 5 minutes, then mark into slices. Leave to cool completely, cut and remove from the tin.