This study developed a synchronous scaffolding environment for teaching technical writing that provides process-oriented collaborative writing supports and practices. This study also examined the effects of the system on EFL (English as a Foreign Language) students' collaborative writing experiences. In the experiment, a "process writing wizard" was created to guide students to complete an essay using comparison and contrast as the rhetorical form. The system provides step-by-step scaffolding guidance and allows multiple students to work synchronously on collaborative writing via Internet. To investigate the learning experiences of the students, five constructs - perceived ease of use, perceived usefulness, attitude to use, intention to use, and perceived response time from peers - were employed to examine if students feel comfortable in the multi-task, multi-user environments. The experimental results are encouraging in that they are consistent with the research propositions. The students also show positive continuing motivation to use the proposed system in future writing tasks.