On 4 October 2015, Cooper was a member of the Cowboys' Grand Final winning side, starting at second row in the side's 17–16 victory over the Brisbane Broncos.
ˌɔn fˈoːɹ ɑːktˈoʊbɚ tˈuː θˈaʊzənd fˈɪftiːn, kˈuːpɚ wʌzɐ mˈɛmbɚɹ ʌvðə kˈaʊbɔɪz ɡɹˈænd fˈaɪnəl wˈɪnɪŋ sˈaɪd, stˈɑːɹɾɪŋ æt sˈɛkənd ɹˈoʊ ɪnðə sˈaɪdz sˈɛvəntˌiːn sˈɪkstiːn vˈɪktɚɹi ˌoʊvɚ ðə bɹˈɪsbən bɹˈɑːŋkoʊz.