Pedzisa mutsara unotevera: Osoro akamiririra Kenya kaviri pachikuva chenyika muna 1991, achimhanya pa1991 IAAF World Cross Country Championships (kwaakauya wechishanu mumakwikwi akareba) uyezve munzira pa1991 World Championships muAthletics (achibviswa mumakwikwi emamita zviuru zvishanu nemuganhu mudiki kuna Dionísio Castro). Zvisinei, akahwina menduru mumakwikwi emamita zviuru zvishanu mumutambo weAll-Africa Games wegore iroro ra1991. Akaonekwa muchikwata cheKenya cheWorld Cross Country kechipiri pa
1992 IAAF World Cross Country Championships, kunyange zvazvo akanga asina kubudirira zvikuru mukuedza uku sezvo akapedza ari panzvimbo yechi23. Pakati pekubuda kwake mudunhu, akakunda muBelfast International Cross Country meet.