Purpose: This paper investigates the accuracy order of grammatical morphemes followed by Saudi EFL learners. The major aim of the research was to reveal the pattern of grammatical morpheme acquisition of the participants, and to compare it against the Natural Order Hypothesis (NOH) as stated by Krashen (1977). The different factors that affected the generated order were also discussed. Research Methods: The present research adopted a descriptive quantitative design. Three groups of male and female students (n= 258) participated in the study. The participants were selected randomly from public schools and university colleges. They responded to a grammar elicitation task designed to test their accuracy of using grammatical morphemes. Pica's (1983) TLU method was used to assess the participants' performance. Findings: It was found that Saudi EFL learners developed the accuracy of using grammatical morphemes in a similar sequence regardless of their educational stages. Although this sequence was fixed, there seemed to be a clear effect of the educational stage upon the quality of their usage. The generated accuracy order was found to be different from the NOH. This result suggested that the participants' first language (L1) affected the accuracy order of grammatical morphemes. Implications for research and practice: The findings of the study suggested that course book lesson plans should be designed according to the generated order to facilitate grammatical morpheme acquisition. Further research that will utilize a bigger size of samples is also required to confirm the generated order.