You cannot easily do a GPA like one can do for creators. You can still search for all nfts in a collection when parsing all collection transactions.

It is possible with [metaboss][1] where an indexer is used or by parsing the transactions like in this metaplex rust and typescript [examples][2]. 


  [1]: https://metaboss.rs/collections.html#get-items
  [2]: https://github.com/metaplex-foundation/get-collection