Kammala jumla mai zuwa: A cikin kakar 2015/16, Cowen ya yi gwagwarmaya don ƙarfafa kansa a cikin Ottawa, wani lokacin yana ganin kansa yana da kyau. A ranar 9 ga Fabrairu, 2016, an haɗa Cowen a cikin cinikin 'yan wasa tara tare da Toronto Maple Leafs. Cowen, Colin Greening, Milan Michalek, Tobias Lindberg da kuma Ottawa ta
An aika da zagaye na biyu na zagaye na 2017 zuwa Toronto a musayar kyaftin din Maple Leafs Dion Phaneuf, Matt Frattin, Casey Bailey, Ryan Rupert da Cody Donaghey. A ranar 26 ga Fabrairu, 2016, Maple Leafs ya sanya Cowen a kan 'yanci sannan kuma aka sanya shi ga AHL da ke da alaƙa da su, Toronto Marlies. Daga nan ne Toronto ta aika da Cowen gida don jiran sayan kuma an ba shi 'yanci don tuntuɓar sauran ƙungiyoyi game da sabon kwangila don kakar 2016-17; siyan kwangilar Cowen zai samar wa Leafs da bashin $ 650,000 na albashi don kakar 2016-17.