He is best known for his Real Valladolid stint, spending the better part of his professional career in Spain, appearing in 206 official games in representation of three clubs.
Peternac spent five seasons at Real Valladolid, appearing in 171 competitive games and becoming the team's all-time top goalscorer in La Liga.
His goal total also made him the second-highest Croatian goalscorer in the competition, behind Sevilla FC and Real Madrid's Davor Šuker.
On 19 May 1996, in an 8–3 away win against Real Oviedo which proved crucial in helping Valladolid avoid direct relegation in 1995–96, Peternac set a club record by netting five times, four of which on penalty kicks.
He was then loaned to Real Murcia,[4] where he played one season in the second division before closing out his career back with the Aragonese (one match, followed by retirement due to injuries).