At the College of Philosophy and Theology the Bischoefliches Lyzeum, a centre of scholastic renewal, Grabmann was influenced by his teacher Franz von Paula Morgott (1829-1900) to study the work of Thomas Aquinas.
In August 1895, Grabmann entered the Dominican novitate at what is now Olomouc in the Czech Republic, but he left six months later to pursue the secular priesthood.
Grabmann was an alumnus of the Collegium Divi Thomæ de Urbe, the future Pontifical University of St. Thomas Aquinas Angelicum in Rome (Italy).
The first of his great works, Die Geschichte der scholastischen Methode, in two volumes, 1909 and 1911 made extensive use of unpublished medieval texts.
There, he completed pioneering research on the history of Aristotelianism in the 13th century which was published in 1916 as Forschungen über die lateinischen Aristoteles-Übersetzungen des XIII.
According to Battista Mondin, Grabmann interprets Aquinas' metaphysics as an advanced version of Aristotle's based on the notion of common being (ens commune) and his rational theology as employing an original concept of being to describe the Divine attributes based on the notion of subsistent being itself (esse ipsum subsistens).