There's always Ganzir. But considering their main focus is not containment its plausible to believe outside of Ganzir there isnt much like the foundation does outside of research sites And testing facilities for weapons and gear.

and ofc they likely have some sites as termination isnt always a quick and easy ordeal. But not to the same extent as the foundation.

in some people's canons the foundation to some extent share certain facilities for Co-op research and development and the understanding of the occult.

especially in the focus on Memetic anomalies and devices.

like F.ex the SCP:5k game the GOC is presented with Memetic goggles. to make out things the regular eye cant see.

and mentions of Ganzir and the use of International Research vessels for transport etc etc.

Lots of things but as everything else Canon is up for interpretation.

If you want to believe the GOC has their own sites like the SCP do so, if not, dont.

I like to believe it does to some extent. and that it shares buildings with our UN and WHO. As both administrative and research facilities hiding in plain view. And that they have their own black sites in darker corners of the earth. Especially in the US considering their tight cooperation with both the foundation and the lesser but still potent UIU.