The lack of opportunities to practice the English language outside the English as a Foreign Language (EFL) classroom can prevent English language learners (ELLs) from promoting their language proficiency to high standards. This lack makes the progress from one level of English to the next one a hard mission for Arab students. Subsequently, students' mastery of the English language is often not expected to occur without frequent practice and organized formative assessment. To enrich such methods of assessment, a mobile-assisted language learning (MALL) technique was adopted in a classroom formative assessment for holistic language proficiency of listening, vocabulary, and grammar to determine whether it would make a difference in results. For fourteen weeks, this quasi-experiment consisting of a pre-post-test one group design was carried out over two cycles of seven weeks each, with 598 participants. During the experiment, students practiced formative assessment conventionally during the first cycle, while this assessment was done with the medium of two mobile apps: Kahoot! and Quizizz during the second cycle. The results of the Oxford Placement Test (OPT), replicated as the pre-test and post-test, indicated that mobile-assisted formative assessment resulted in a statistically-significant positive influence of using mobile apps on students' overall language proficiency.