Originally Posted by
QueEff
Sometimes if you search the QF site for business you will find a "first Sale" column in addition to the business options, you can book mixed that way if your dates allow it.
In my experience even if the QF website displays both business and first class options it will not actually let you select first one way and business the other. There is logic in the website booking engine that greys out the class for the return flights that is opposite the class selected for the outbound flights.