As governments, donors and implementation organisations re-focus Education for All Goals in terms of quality of education, increasing concerns have been raised over low literacy levels in developing countries. This paper provides key learning from the application of an early reading intervention applied in post-conflict Liberia, which included a robust assessment tool (Early Grade Reading Assessment) to measure the impact of the programme on students' reading levels. A rationale for the design and methodology applied by the two implementing organisations (Research Triangle Institute (RTI) and Concern Worldwide) is provided, situated within the Liberian education context. The paper demonstrates the positive impact on programme quality, contextual relevancy and scale-up that a diagnostic baseline assessment has when linked to a tailored literacy intervention. Lessons learnt are presented to guide the identification of best practice in early literacy interventions at national-level and internationally. (Contains 2 tables.)