Gregory was considered a supporter of Andrew II of Hungary, then Béla IV of Hungary. He actively participated in their governance at the royal council. He led a royal campaign against the Teutonic Knights in 1225, who had attempted to eliminate the suzerainty of the Hungarian kings in their granted territory Barcaság (now Țara Bârsei, Romania) in Transylvania. During his episcopate, Gregory managed to resettle the Franciscan and Dominican friars in the Diocese of Győr. He successfully petitioned Pope Gregory IX in order to recover the previously usurped church benefice by Andrew II. During the Mongol invasion of Hungary, Gregory participated in the Battle of Mohi on 11 April 1241, where he was killed, according to Master Roger's "Carmen Miserabile", where his name was misspelled "George".