USPSTF Transparency and Accountability Act of 2019 This bill imposes additional requirements on, and otherwise revises provisions related to, the U.S. Preventive Services Task Force. The task force must (1) develop and publish research plans that include specified components to guide its review of scientific evidence relating to the effectiveness of preventive services; (2) publish in the Federal Register a request for comments on research plans, evidence reports, and recommendations; and (3) convene a preventive services stakeholders board to provide feedback and recommend preventive services and scientific evidence for the task force to review. The bill also provides statutory authority for the task force's system for grading preventive care (Grades A, B, C, and D and a Grade I for insufficient information). In addition, the bill revises the authority of the Centers for Medicare & Medicaid Services (CMS) to modify Medicare coverage of certain preventive services when the modification is based on a task force recommendation. Specifically, the CMS may modify coverage based on a task force grade or recommendation only if it was developed or updated in accordance with this bill and if the CMS agrees with it after consulting with other agencies and stakeholder groups. Certain Medicare quality measures related to a recommendation of the task force may similarly only be applied under these circumstances.