Osoro akamiririra Kenya kaviri pamutambo wenyika muna 1991, achimhanya muIAAF World Cross Country Championships muna 1991 (kwaakauya wechishanu munhangemutange refu) uyezve mumutambo we 1991 World Championships muAthletics (achibviswa mumakwikwi emamita zviuru zvishanu nemusiyano mudiki kuna Dionísio Castro). Zvisinei, akahwina menduru mumakwikwi emamita zviuru zvishanu mumutambo weAll-Africa Games wegore iroro ra1991. Akaratidza muKenya World Cross Country chikwata kechipiri panguva 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.