By the time archaeologists inspected the site in 1997, it was already heavily overgrown and difficult to distinguish as a structure at all. What they were trying to read was a wedge tomb, a type of megalithic chamber burial characteristic of the later Neolithic and earlier Bronze Age in Ireland, typically consisting of a roofed stone gallery that widens and rises toward its open end. At Cooleabeg, even that basic form had become obscured, its stones scattered, toppled, or absorbed into a later field boundary.

The most detailed account of the monument comes from Ruaidhrí de Valera and Seán Ó Nualláin, whose 1961 survey of the megalithic tombs of County Clare recorded the site while more of it was still legible. At that time, the tomb sat within a low earthen mound roughly eight metres in diameter, though a later east-west field wall had been driven straight through it, and the northern sidestone, measuring around 2.45 metres in length, had been incorporated into that wall, leaning southward at about 45 degrees. The southern sidestone appears to have broken into at least two pieces, one of which has a dressed edge. Three further slabs lie displaced to the west of what would have been the chamber, and the largest of these, some 3.4 metres long and tapering from 2.6 metres wide at its western end to 1.7 metres at the eastern, is considered the likely roofstone. De Valera and Ó Nualláin could not establish the chamber's original dimensions with certainty, but their plan suggested an interior roughly 2.5 metres long, oriented toward the south-southwest, and narrowing from about 2.3 metres wide at the open end to around 1.3 metres toward the rear. The low mound surrounding the structure may conceal the remains of a stone cairn beneath the earth, as was found during excavations at wedge tombs in the nearby townland of Parknabinnia. A second wedge tomb survives in the neighbouring townland of Colleamore, visible approximately 940 metres to the east-southeast, suggesting this part of Clare once held a meaningful concentration of such monuments.