It will be the first time the sides have met since the opening round of the 2012 Olympics when the eventual silver medallists secured a frenetic 79-78 victory with Jose Calderon scoring the decisive free throws in the final minute.
Although LA Lakers forward Pau Gasol and FC Barcelona star Juan Carlos Navarro have taken the summer off, the hosts retain NBA All Star talent in Memphis Grizzlies centre, Marc Gasol, as well as a host of other leading lights from both sides of the Atlantic.
20-year-old van Oostrum, GB's youngest player who has spent the past four seasons with leading Spanish club Baskonia Vitoria, admits it is the ultimate test but is relishing the opportunity to see how he, and GB, stack up.
"Obviously I'm really excited to play against a big team like Spain," said the point guard from Sheffield. "With me playing in the ACB, a lot of people are going to watch me.
"We watched them play against France (on Monday) and it was an amazing game. Even without those two players, they're still far and away the second best team in the world."
GB head coach Joe Prunty brings back Liam Potter into his squad after the Grimsby-born centre missed last weekend's defeats to Sweden and Poland.
And Wednesday's game will also see captain, Drew Sullivan, make his 100th international appearance in the colours of both England and GB.
"He's a key part of our team," van Oostrum said. "We need that experience and he's our main leader, the guy who helps out with everything. To have him reach his 100th appearance is a great accomplishment."
Following the two games, Prunty will name his 12-man roster for EuroBasket with the Standard Life GB team facing Israel in their opening first round game in Ljubljana on 4 September.