Cooperative Purchasing allows eligible entities (state, local, and tribal governments) to purchase from approved industry partners, at any time, for any reason, using any funds available. - U.S. General Services Administration​

Co-op Purchasing allows eligible customers to streamline the procurement process by skipping the bidding process and going directly to an approved/preferred vendor.

"With cooperative purchasing, one agency — sometimes referred to as the cooperative purchaser — goes through the bidding process and awards a contract to a vendor. Other government organizations — and in some instances, non-profits— can then piggyback off of this contract" - Holly Welles: 'The Economic Benefits of Cooperative Purchasing'