This essay stresses the importance of infusing a developmental perspective into the design, implementation, and evaluation of parent-focused language interventions to promote young children’s language success. Guided by Waddington’s (1957) heuristic image of the “epigenetic landscape” and drawing on empirical research, we propose eight premises about early language development and illustrate how each premise might inform interventions. Three premises address the developmental pathways to language; two highlight the essential role of the environment. The final three premises focus on the child and parent as the essential developmental unit and on the collaborative, transactional, developmental processes that facilitate language acquisition. These premises suggest that intervention should begin well before first words, address the social foundations of language, and support parents in their unique role as they directly and indirectly immerse children in the developmental landscape of language intervention.