There are two opportunities for cycling/camping weekends in October. The first is Fall Fling, Oct 8 & 9 at Okmulgee State Park. See details here.
Next comes Tour de Trees at Lake Eufaula State Park, Oct 22 & 23. Details for this ride can be found here.
All OBS cycling/camping weekends are free, but each participant is responsible for his/her camping fee and food.