Kosič made his debut for Slovenia on 18 November 1992 away against Cyprus, coming on as an 80th-minute substitute for Zlatko Zahovič,[3] and earned a total of five caps until his final appearance in 1994.

[4] Between 2006 and 2017, Kosič managed ATUS Ferlach, Olimpija Ljubljana, Triglav Kranj, and the Slovenia under-17 national team.

[5] In the 2019–20 season, Celje won their first-ever Slovenian championship.

[8] However, he left the club on 21 December 2020 after Celje finished the first part of the 2020–21 season in seventh place.

[9] On 9 September 2021, Kosič was appointed as manager of Tabor Sežana, signing a contract until 2023.