This study investigates the impact on extemporaneous English-language first drafts by using Google Translate (GT) in three different tasks assigned to Chinese sophomore, junior, and senior students of English as a Foreign Language (EFL) majoring in English. Students wrote first in Chinese (Step 1), then drafted corresponding texts in English (Step 2), and translated the Chinese into English using the 2016 GT version (Step 3), and finally compared their self-written (SW) English texts drafted in Step 2 and their GT English texts translated from the Chinese texts in Step 3. Both English drafts were analyzed using two types of online computational assessments to compare and evaluate grammatical components of writing quality and lexical features. Results indicate that the GT English texts presented a number of components of significantly higher writing quality than those of students' SW texts, by having more words, fewer mistakes in spelling and grammar, and fewer errors per words. In addition, there were more advanced-level words in the students' GT texts than in their SW ones. A follow-up questionnaire survey indicated that EFL students found satisfaction with using Google Translate in their English writing, especially in finding vocabulary items and enhancing the completion of English writing.