Off-Site Construction (OSC) is a new construction method based on factory production. Due to its advantages over traditional methods, such as high productivity, economic efficiency, and excellence in quality, OSC research has actively been conducted worldwide ranging from design and production standardization, transportation method, to construction planning. Thus, to understand what knowledge has been developed to improve the management of OSC projects, this study reviewed OSC papers that focus on improving a specific project management area (e.g., time, cost, and quality) in a specific phase of a project, i.e., “process-level research.” This study found 94 papers with such a focus, out of 222 OSC project management papers published from 1986 to 2018, and assessed the trends of the research with multiple dimensions, including project phases, OSC types, application types, and management areas. Main findings are as follows: (1) process-level research has been increasing fast since 2006. (2) Non-volumetric pre-assembly type contributes the most to the increase of process-level OSC management research. (3) Research focuses vary depending on the application type (e.g., living quality issues for residential, economics issues for non-residential, productivity issues for plant). (4) Wider project management areas (e.g., quality, human resources, risk) have gained attention from OSC papers since 2006. (5) Non-volumetric type gained interests in residential and non-residential buildings, whereas modular type was studied frequently in plants. This study would help project management researchers understand the trends in OSC and plan and conduct future OSC project management research.