Bruce specialises in vertebrate palaeontology, biostratigraphy, sedimentology, basin development and palaeo-environments. His main area of interest is the early therapsids (particularly anomodonts, biarmosuchids and dinocephalians) and he also has an interest in temnospondyl amphibians.
Bruce and his students have researched dicynodonts from throughout the Karoo Supergroup, but his particular speciality is on the tetrapod fauna and basinal development of the rocks of the lowermost Beaufort. Here he has discovered a new primitive and ancient therapsid fauna in South Africa which is similar to the most primitive therapsids from Russia and China.