The 18-year old winger was signed to a five-year deal along with Roar teammates Michael Zullo and Adam Sarota who signed three-year deals.
The trio were signed as a package deal believed to be worth about $1.8million which is a handy pick up for the Roar although they will be losing three of their most promising players.
Ex-Roar and Australian national team coach Frank Farina believes Oar’s decision to take a shot in Europe could work well for him, especially when it is selection time for Pim Verbeek’s 23-man Socceroos World Cup squad.
"It will come as no surprise to see Oar's name read out when Pim names his World Cup squad," Farina said.
"He's only young, has his feet firmly planted on the ground, but more importantly has all the attributes to become a really great player. While Zullo and Sarota are a little older, I think all three will thrive in the Dutch environment."