Before its excavation between 1969 and 1973, the tomb was so buried beneath collapsed cairn stones that its true form remained a mystery. What emerged from five seasons of careful archaeological work was a sophisticated megalithic structure: a 36.5 metre long cairn that narrows from 13.5 metres at its northern end to 10.5 metres at the south, reaching a maximum height of 2.3 metres behind the gallery. The monument faces upslope towards the head of the valley, its northern end featuring a court that would have measured approximately 10 metres in length and at least 8 metres in width, leading to a two chambered gallery with an additional subsidiary chamber opening onto the western side of the court.

The gallery itself showcases remarkable construction techniques typical of Neolithic builders. Entry is gained through matched transverse jambs set 0.8 metres apart, topped by a substantial lintel measuring 2.2 metres by 1.25 metres. Beyond this entrance, the space is divided into two chambers by another set of jambs with their own lintel above. The front chamber measures 2.6 metres long by 2.7 metres wide, whilst the rear chamber extends 2.7 metres in length, narrowing from 3 metres wide at the front to 2.3 metres at the back. Each side of the gallery consists of three orthostats, with the middle stones cleverly overlapping the segmenting jambs to serve both chambers; an arrangement also found at the nearby Shalwy tomb. Tiers of corbelling survive along the sides and back, whilst dry wall revetment, though now mostly reduced to a single course, once lined the cairn’s edges.

The artefacts recovered during excavation offer tantalising glimpses into the lives of those who built and used this tomb. Among the finds from the chambers were two heat shattered flint plano convex knives, a classic flint hollow scraper, and a concave scraper. The 1971 season, which focused on excavating the court and determining the cairn’s original extent, yielded numerous flint flakelets alongside finished implements including two end scrapers, a hollow scraper, and two knives. These tools suggest the tomb served not just as a burial place but as a focal point for ritual activities that involved the working and deposition of flint implements, connecting An Chruach Bheag to the broader tradition of court tomb construction that flourished across northern Ireland during the Neolithic period.