An important part of the post-excavation works was the analyses of carbonised archaeobotanical remains. 

The charcoal assemblage from the larger Neolithic hall was overwhelmingly dominated by oak, which made up over 90% of the charcoal identified from this structure. When just the exterior post-hole fills are considered, oak forms 94% of the identified charcoal. The only other type of charcoal that has any significant representation in this structure was alder (7% of all charcoal). It is probable that at least some of this oak is the remains of structural timbers and that the hall was built from oak posts. This would correspond with the charcoal assemblages recovered from other Neolithic halls in Scotland, which have been suggested as destroyed by fire. If that also occurred at Carnoustie, then it may be that this hall did not have any significant amount of hazel wattle as walls or internal divisions as it would be expected that much more hazel charcoal would have been recorded from the structure if hazel had formed a significant part of the structure. It is also likely that oak was the main fuel source used in this Early Neolithic Hall.  Oak was the dominant tree type present in lowland broadleaved woodland during the Neolithic and so would have been readily available for both building structures and burning in hearths.

While cereal grains were not abundant in the larger Neolithic Hall, naked barley, emmer wheat and bread wheat were all represented. Naked barley, often with emmer wheat, is strongly associated with Neolithic sites in Scotland. The combination of emmer wheat, bread wheat and barley is also recorded from other Neolithic timber halls in Scotland. Bread wheat is very rare in the Scottish prehistoric archaeobotanical record but is abundant in Germany and Denmark during this period. It would seem that bread wheat was not commonly grown or eaten during the Neolithic in Scotland but its presence in features from Neolithic timber halls suggests that it may be associated with the status and function of these particular types of structures. There is no evidence for crop weeds or crop processing waste in any of the samples and so this might indicate that only fully cleaned grain was being brought into the structure. The only other evidence for food plant remains from the larger Neolithic Hall at Carnoustie were carbonised hazel nutshell fragments and a few apple pips. Hazelnuts were a readily available food resource but apple pips are very rare in the Scottish archaeobotanical record.

The archaeobotanical evidence indicates that the smaller Neolithic hall at Carnoustie was built from oak but, again, there is little evidence for any substantial use of hazel wattle in the structure. The main difference between the carbonised assemblages is that there were over 8 times as many cereal grains in the smaller Neolithic hall than the larger. 35% of the cereal grains were identifiable as barley with 12% identifiable as naked barley. The remaining grains were wheat, with a few further identifiable as emmer wheat but no bread wheat was found in this structure. No crop weeds or chaff were identified either.