He had an important role in the renewal of the Biblical studies in France with his books, Introduction aux Livres Saints ("Introduction to the Holy Books", 1954) and Pages Bibliques ("Biblical Pages", 1954), which were reissued several times and had translations in several different languages.

[citation needed] Grelot was a counselor of the Bishops' Conference of France and a member of the Pontifical Biblical Commission, from 1972 to 1983.

[citation needed] He participated in the TV series Corpus Christi (1997), exhibited at the Arte channel, about the Gospels.

[citation needed] He was quoted by Pope Benedict XVI in his book Jesus of Nazareth (2007).

[1] He had controversies with other biblical scholars who opposed a late dating of the New Testament writings; he wrote his book L'origine des Évangiles (1985) in opposition to the view held by Jean Carmignac.