The breed resulted from the crossing of the Wiltshire Horn, Suffolk, Hampshire Down, Poll Dorset, Lincoln and English Leicester sheep breeds.

These rams are used as terminal sires for prime lamb production.

Coolalee sheep have shown considerable promise in an independent central progeny testing system for prime lambs.

The system is designed to identify outstanding meat sheep sires and their ability to sire elite lamb with a carcase weight of more than 22 kg and a fat score of 2–3.

The testing also showed significant reductions in fat depth, which is an important consumer requirement, on first cross Coolalee lambs.