What is the collective noun for brigade?

There isn't a specific, established collective noun for "brigade." However, depending on the context, you could use:

General terms:

* A force of... (e.g., a force of soldiers, a force of firefighters)

* A group of... (e.g., a group of soldiers, a group of firefighters)

* A company of... (e.g., a company of soldiers, a company of firefighters)

More specific terms:

* A battalion of... (if the brigade is a military unit)

* A contingent of... (if the brigade is a temporary unit)

Ultimately, the best choice depends on the specific context and the desired level of formality.