The purpose of this study was to find out, whether three methods of presenting input, were effective in relation to language aptitude. Persian-speaking learners of English were provided with 20 grammatical collocations (verb-preposition collocations) embedded in authentic passages, lexically/grammatically elaborated passages, and lexically/grammatically elaborated passages with shorter sentences and enhanced target collocations. Participants were assessed on their receptive knowledge and productive knowledge of the grammatical collocations by a posttest and a delayed posttest, and their scores were correlated with various measures of language aptitude. The results suggested that modified elaborated input, which provided more focus on form (FonF), positively affected immediate and long-term gains in receptive knowledge and ruled out individual differences (IDs) in language aptitude. The results also implicated working memory (WM) as an explanatory variable in immediate and long-term achievements in productive knowledge under all the conditions of presenting input.