The striker began his professional football career in the city of his birth with RC Strasbourg, where the fans soon nicknamed him the "angel of la Meinau" (L'ange de la Meinau; Engel von der Meinau, Meinau is the stadium of the club). Briefly after first playing for Strasbourg (May 1960) the team were relegated to the second division, but returned after one year to Division 1, where Gress played until 1966 and his departure to VfB Stuttgart. Strasbourg were at the time only in mid-table of the division, but won the 1966 Coupe de France.