He made his league debut on 15 March 1992 coming on as a substitute in the late minutes of a 1–0 win against FC Blau-Weiß Linz.
[11][12] Osei moved to Germany and transferred to Eintracht Frankfurt in 1993, in the process joining his Ghanaian colleague, former teammate at Okwawu United and cousin Tony Yeboah.
[14] After leaving Caracas FC, Osei joined Mainz 05 in 1996 and in the process being in the same squad and playing alongside people like German coach Jürgen Klopp, Torsten Lieberknecht, Bruno Akrapović, and Dimo Wache.
[21] He played alongside players like Emmanuel Armah, Frimpong Manso, Abedi Pele and James Kwesi Appiah within that period.
He later joined his former club Asante Kotoko as an assistant coach to Dramani Mas-Ud Didi ahead of 2013–14 Ghanaian Premier League.
[23] He served in that capacity until the following season when Zdravko Logarušić was appointed as head coach and he moved back into his initial role as the assistant of the club.
[3][28] Osei joined Dansoman-based side Liberty Professionals in May 2017 on a two-year contract as head coach mid-way of the 2017 Ghana Premier league season after the club was experiencing a bad run of matches.
[36][37][38] In August 2021, after Bibiani Gold Stars gained promotion into Ghana Premier League from the Division One League for the first time in the club's history, Osei was appointed the head coach of the club after Kobina Amissah resigned.
[39] Osei was cousins with former Ghanaian international footballer Tony Yeboah, who he played with at Okwawu United and Eintracht Frankfurt.