This report presents key findings from the four years of the Quality Support Program (QSP). The QSP is an initiative of, and funded by, the New South Wales (NSW) Department of Education Early Childhood Education Quality Assurance and Regulatory Services Directorate (NSW DoE), involving the delivery by Australian Children's Education and Care Quality Authority (ACECQA) of free tailored professional development and support to approved providers and service leaders of eligible services across NSW. The QSP has been implemented in four stages, with each stage comprising separate groups of services in 'rounds' of up to 18 weeks of tailored support. These rounds have overlapped with each other. This report covers Stages One to Four. The objectives of the QSP are to improve the quality of participating services so they receive a rating of Meeting NQS or higher, and to improve participants' knowledge of and confidence in the NQS and assessment and rating. Participants were provided with bespoke resources, a QSP facilitator to answer questions, discuss improvement priorities and through a coaching approach prompt critical reflection, and provide one-on-one targeted tailored support with continuous quality improvement. The structure of each QSP round consisted of introductory workshops, provision of eLearning modules and other resources, service visits, support phone calls, video coaching calls, and emails. Workshops and service visits were conducted in-person in Stages One and Two and mostly online in Stage Three and Four due to COVID-19 restrictions. Different service types presented with different contexts and support needs. The QSP drew on the insights of participants to produce service-type specific resources. [For the report from Stage Three, see "Supporting Quality Improvement in Education and Care: Quality Support Program Stage Three -- Key Findings" (ED622370).]