Rubuta ci gaba don wannan sakin layi - Forrest ya taka leda a gasar cin kofin duniya ta FIFA U-20 ta 1987 kuma ya fara bugawa babbar kungiyar Canada wasa a watan Mayu 1988 da Chile. Ya sami wasanni 56 (ban da wasan Mayu na 1990 na Arewacin Amurka da Amurka), mafi yawan kowane mai tsaron gida a tarihin kungiyar kwallon kafa ta kasa da ke da nasaba da Pat Onstad kuma ya sami mafi yawan shafuka masu tsabta a tarihin kasar kafin ya yi ritaya daga kwallon kafa a 2002. Babban aikinsa na kasa da kasa ba tare da wata shakka ba ya taimaka wa Kanada ta lashe gasar cin kofin CONCACAF ta 2000
, wanda aka nada Forrest MVP na gasar da kuma Goalkeeper mafi mahimmanci don ba da izinin kwallaye uku kawai da kuma dakatar da hukunci biyu a wasanni biyar na kungiyarsa. Har ila yau, a lokacin da ya yi aiki na kasa da kasa, Kanada ta samu nasara a kan Brazil kawai wata daya kafin gasar cin kofin duniya a Amurka a shekarar 1994. Forrest ya ci gaba da samun nasara a kan Brazil a shekara ta 2001, inda ya rubuta takarda mai tsabta a cikin 0 <unk> 0 a gasar cin kofin 2001 a Japan. A cikin 2012, magoya bayan sun zabi Forrest a cikin mafi kyawun XI na Kanada a cikin shekaru 100 na farko na CSA.