Most of the bigger names (WB, EA, Square Enix, etc) have a hybrid model. They have inhouse QA, and then for milestones and important phases they also hire external QA, which usually costs less for more people than internal QA. Basically to have more eyes to cover areas in more detail, and also to have the external QA to all the shitty super repetitive tasks everyone hates doing.<br><br>This changes by studio, by project even by milestone.