The Measuring Early Learning Quality and Outcomes (MELQO) was a large-scale study that used specific instruments to provide national-level data on the quality of pre-primary education and children’s development and learning at the start of primary school. It aimed to strengthen attention and investments in quality early childhood education. The study was conducted in Tanzania (Mainland and Zanzibar). It marked the first large-scale application of MELQO globally and contributed to advancing the work of the global MELQO initiative by strengthening global knowledge and discourse on quality pre-primary education.