Grant Reporting Efficiency and Agreements Transparency Act of 2019 or the GREAT Act This bill requires the establishment and use of data standards for information reported by recipients of federal grants. The bill requires the Office of Management and Budget, jointly with the executive department that issues the most federal grant awards, to (1) establish government-wide data standards for information reported by grant recipients, (2) issue guidance directing federal agencies to apply those standards, and (3) require the publication of recipient-reported data collected from all agencies on a single public website. Each agency shall ensure its awards use the data standards for future information collection requests.