Online and Blended Learning (OBL) is well-known for its capacity to lower accessibility and flexibility barriers to traditional education. In the past two decades, this mode of learning has had far-reaching and long-lasting consequences in the realm of education. Covid-19 has made online and blended learning especially important solutions in the context of social distancing while schools still need to ensure that the learning of all students at all levels is not interrupted. Therefore, this chapter aims to provide a thorough literature review on the role of OBL in the new era, requirements, new approaches, and best practices of quality assurance in online and blended learning as well as different methods to evaluate teaching effectiveness in this mode of learning. Moreover, the status of OBL implementation in the Vietnamese context, especially the post-Covid-19 period with the effects from the state policies, and regulations from the Ministry of Education and Training and educational institutions will be figured out to show the challenges in the process. Then recommendations to better implement OBL in Vietnam will be proposed. Theoretically, this chapter will contribute to the current literature review about quality assurance in OBL while practically, it gives hands-on techniques and best practices for policy-makers, quality assurance staff, as well as educational managers and teachers to implement at their schools.