Young children's exposure to early math concepts is important in their development, in their confidence in math skills, and in their ability to use math later in life. In 2013, the Heising-Simons Foundation embarked on an innovative path to support children's early math development. The Foundation invited several family engagement providers to develop, test, and integrate research-based early math projects within their existing family engagement programs. The Foundation has since supported two providers--Reach Out and Read (ROR) and the YMCA of Silicon Valley (YMCA)--as they refined their early math projects and scaled them up in new sites. Mathematica conducted an implementation study that examined the scale-up effort during 2018 and 2019. We share the study findings in this brief so program operators, practitioners, and policymakers interested in scaling up early math programs can benefit from the experiences and lessons learned from these two pioneering organizations.