The curriculum for teaching undergraduate university students in Iran majoring in English generally includes paragraph writing in the second year and essay writing (4-5 paragraphs) in the third year. The first-year course 'Grammar and Writing (I & II)' offered in two consecutive semesters covers grammar only, despite the inclusion of writing in the title, and rarely goes beyond sentence-level writing in support of the newly taught grammar. This one-year delay in focusing on writing per se has been a source of frustration for those students who have to deal with the demanding writing tasks or large-scale written assignments such as extended essays and papers later during their academic or professional life. The current study describes and evaluates a teaching intervention for the potential development of a writing curriculum in first-year writing classes. A pre-test-post-test control group design was employed to compare the effect of the writing instruction within the process genre approach with that of the traditional grammar and sentence-level writing on the fluency, accuracy and quality of students' (n = 68) paragraph and essay writing during two consecutive semesters. Findings from the tests and a focus group discussion revealed that students in the treatment group outperformed their control group counterparts at both paragraph and essay levels. The findings could inspire similar EFL programmes to design a writing curriculum and instruction commensurate with the real needs of their students.