The spread measures roughly twenty metres north to south and just over twenty-three metres east to west, a modest rise in the earth that most people working the field around it would pass without a second glance. It is the characteristic burnt material beneath the surface that gives it away as a fulacht fia, a type of prehistoric cooking site found in large numbers across Ireland and Britain.

Fulachtaí fia, the plural form, typically consist of a horseshoe-shaped mound of fire-cracked stone accumulated beside a trough and a nearby water source. The working theory, broadly accepted among archaeologists, is that stones were heated in a fire and then dropped into a water-filled trough to bring it to boiling point, a process that fractures the stone repeatedly until it becomes useless and is discarded to form the mound. The presence of a stream to the west of the Rathcooney site fits this pattern neatly, since a reliable water source was essential to the process. Most fulachtaí fia date to the Bronze Age, roughly 1500 to 500 BC, though examples from other periods are known. Beyond cooking, some researchers have proposed uses ranging from textile processing to bathing, and debate about their precise function has never entirely settled.