There is a growing consensus that implementation of evidence-based intervention and treatment models holds promise to improve the quality of services in child public service systems such as mental health, juvenile justice, and child welfare. Recent policy initiatives to integrate such research-based services into public service systems have created pressure to expand knowledge about implementation methods. Experimental strategies are needed to test multi-level models of implementation in real world contexts. In this article, the initial phase of a randomized trial that tests two methods of implementing Multidimensional Treatment Foster Care (an evidence-based intervention that crosses child public service systems) in 40 non-early adopting California counties is described. Results are presented that support the feasibility of using a randomized design to rigorously test contrasting implementation models and engaging system leaders to participate in the trial.