An intricate area in EFL for many Lebanese Arabic speaking learners I’ve met is the proper use of English verbs. Their essays usually reflect a systematic use of verbless sentences, erroneous tenses, and transliterated expressions that might alter the whole concept of the intended communication. The aim of this study is to map the erroneous use of English verbs in essays written by Lebanese third secondary EFL learners, to analyze the source of these errors, to correlate it to the social influence, the transfer from their native language, Modern Standard Arabic, and to contribute to EFL research in the Lebanese context. To analyze errors of the corpus data quantitatively and qualitatively, Error Analysis, an important technique in the field of second language acquisition based on Ellis & Barkhuizen’s (2009) approach was performed. Then errors such as: temporal and modal verb operators, auxiliaries, the infinitive form of verbs, passive voice operator, conditional forms, were identified, counted, reconstructed, their linguistic taxonomy and surface structure taxonomy was defined. Finally, to determine the source of these errors, verbs in English Functional Grammar (EFG) (Halliday, 2004) and Modern Standard Arabic (MSA) (Ryding, 2010) were analyzed contrastively. The findings revealed that the verbal category formed 35% of all their Interlingual errors. If attention is not turned to the notion of Interlanguage now, our learners will get stuck into fossilization, fail to overcome their weakness; later on, they will be carrying it with them to the university level. Suggestions for how to reconsider modern teaching methodology were addressed to specialized authorities, curriculum designers and EFL teachers.