i have a giant gourami and was wondering if an oscar would work as a tank mate due to similar size
If by Giant Gourami the OP means Osphronemus goramy, I strongly disagree. The only issue is tank size, since the Gourami can get almost twice as large as the Oscar which can get big enough. True Giants easily hang with large Cichlids, including Flowerhorns (which are generally way more aggressive than Oscars) in suitable tanks.i personally wouldn't. i have an oscar and i know for a fact he is too boisterous to live with a giant gourami.
remember to have a separate quarantine tank for any new fish you bring home, and keep them in that tank for at least a month to observe and treat any diseases that may come up. you don't want to risk getting your gourami sick.
If by Giant Gourami the OP means Osphronemus goramy, I strongly disagree. The only issue is tank size, since the Gourami can get almost twice as large as the Oscar which can get big enough. True Giants easily hang with large Cichlids, including Flowerhorns (which are generally way more aggressive than Oscars) in suitable tanks.