OASIS+ is GSA's big multiple-award vehicle for professional services work, the kind of buying that does not fit neatly into a product schedule the way the GSA Schedule does. It is organized into domains covering different types of services, and any federal agency can place orders through it once you hold a seat. As the successor to the original OASIS vehicle, it is the one most large, ongoing services requirements now flow through.

In a sentence

"This requirement will be competed among OASIS+ holders in the applicable domain." As with any multiple-award vehicle, you need a seat in the right category first; the order itself is a second, separate competition among the businesses that already have one.