An option may be to use the Hierarchical Z-Buffer Occlusion. This uses a compute process rather than the hardware queries so can perform better. However it is more conservative so may cause more to be drawn offsetting any savings of the method. You can enable it through the console (it’s not available through the settings window, but can be placed in the render setting block of your DefaultEngine.ini):
r.HZBOcclusion 1
The general reasons for occlusion taking up time is the scene rendering a lot or just the sheer number of occlusion queries. If you use:
stat initviews
You can see a breakdown of what is going on. The Unreal docs covers it all pretty well, so worth going through that if you need to delve more deeply. It’s really down to the nature of your project what approaches to use.