Genetic counselors (GCs) play a pivotal role in selecting clinically appropriate and cost-effective genetic testing. Several single-institution reports over the past decade provide evidence of the value GCs bring to this stewardship role across diverse settings in healthcare, including hospital laboratories, commercial laboratories, and insurance companies. This multi-center, prospective, and quantitative study describes the outcomes of GC review of genetic test requests over a four-week period at six hospital laboratories and three commercial laboratories, thus expanding our understanding of this emerging specialty in the genetic counseling field. This study also highlights the added value of utilizing GC expertise in stewardship efforts, namely selecting the most appropriate genetic testing and realizing significant cost savings. GC review of genetic test requests led to an average order modification rate of 22%-25%. It also resulted in significant cost savings to institutions. The projected average annual savings after GC review of genetic test requests approximated $665,600 for hospital laboratories and $1,651,000 for commercial laboratories. These study findings demonstrate the significant value of GC-led genetic test stewardship programs, allow for comparisons across institutions currently performing genetic test stewardship, and support the implementation of a GC-led stewardship program at institutions who currently do not have one.