|Notes:||Excavated in 1937 as part of a campaign that also saw excavations at Rousay sites including Midhowe, the Knowe of Lairo and Bigland Round.|
The excavation of the cairn took place in early 1937 by workmen of the Trumland estate, overseen by the estate factor James Yorston Jr and directed by the estate owner Walter Grant, in consultation with Dr J. G. Callander.
Very little exists of records made during the excavation, although some photographs were taken after completion of the excavation and a short film made of the excavated site, showing the structure in considerable detail.
The site was not maintained after excavation and now consists of only a few projecting orthostats on rough grassland below Ward Hill, adjacent to the seashore opposite the small island of Eynhallow, and a few hundred metres eastwards of the Midhowe stalled cairn.
The cairn was rectangular, orientated north-west to south-east.
It measured 27.4m long by 5.6 to 6.6m wide. The entrance is suggested to have been in the south-eastern end of the cairn, but the passage and outer part of the chamber had been destroyed – presumably during Iron Age modifications to the site. The centre part of the chamber had been heavily disturbed when it was converted into an earth-house/souterrain.
The northern end of the chamber had also been destroyed.
The excavators found the eight pairs of divisional orthostats remained and the position of a missing pair was established. These were placed to form compartments 1.5 to 1.8m long. If this spacing continued towards the entrance there would have been two more pairs followed by a pair of portal stones, allowing for a passage about 2.6m long.
This would have meant the chamber was approximately 22.2m long, with twelve compartments, and 1.8m in width.
Within the undisturbed compartments was evidence suggesting Rowiegar’s stalls contained the same low, stone shelves, or benches, found between the orthostat dividers in Midhowe.
A large quantity of animal remains were found, along with some human bone fragments. These do not appear to have been studied in detail at the time. In 2002, however, the full (but small) assemblage of human bones from Rowiegar was re-examined. 
The new analysis proposed the remains represented a minimum of 28 people, representing all ages.
Of these there were “seven cases of trauma or possible trauma evident in the skull and two possible cases of trauma in the postcranial skeleton” possibly linked to interpersonal violence.
Malnutrition was also evident in the skeletal assemblage, as well as signs of general bodily stress:
“As most signs of trauma, disease and malnourishment occur in the non-preservable soft tissues of the body, this level of evidence of such population stresses in the skeletal assemblage indicates a high level of violence and ill-health. The times during which these people lived were both brutal and challenging.” 
Radiocarbon dating of the remains suggests the structure was in use between c3300-2900BC, but not necessarily continuously.
Isotopic analysis of the human remains “indicate that these individuals consumed a predominantly terrestrial diet, albeit with some evidence of the possible minor inclusion of marine protein and intra-group dietary variability.” 
Knowe of Rowiegar, Rousay.