Merino genes play an important role in prime lamb production in Australia with the majority of lambs slaughtered containing some proportion of merino genes. The aim of this project was to determine the effect of Merino genetics in prime lamb production systems, extending the outcomes from the Maternal Central Progeny Test. Merino rams influenced some of the profit drivers of the prime lamb business, including the number of lambs weaned and the liveweight, carcass traits and eating quality of terminal cross lambs. There was only a small impact of Merino rams on second cross lamb production. Prime lamb producers will be able to improve prime lamb production by sourcing ewes that have the right phenotype to produce first cross and terminal crossbred lambs. The data collected in this project has also been used in the development of a single Merino database to provide breeding values for Merino producers in traits important for prime lamb production.