In language learning contexts, writing tasks that involve reading of source texts are often used to elicit more authentic integrative language use. Thus, interests in researching these read-to-write tasks in general and as assessment tasks keep growing. This study examined and modeled the process of summary writing as a read-to-write integrated task. Data of test-taking process were collected from 94 Chinese English as a foreign language (EFL) learners who completed two summarization tasks. Seven students first completed the tasks while thinking aloud their mental process. The researcher observed their test-taking process and conducted post-test interviews to learn more about how they completed the tasks. Participants' verbal reports were coded into mental moves, which were then grouped according to their purposes. These formed the basis for identifying the processes and sub-stages participants followed while completing the tasks. Based on the analysis of the think-aloud, observation, and interview data, a questionnaire was developed containing items specifying the processes task takers went through. The questionnaire was completed by the remaining 87 participants to test the generalizability of the findings. A process model of summarization was constructed subsequently. The implications of the study are discussed with reference to construct validity of summarization tasks, EFL writing instruction and assessment.