The correct use of collocations and prepositions plays an essential role in writing. Previous research has demonstrated that students, who master these lexical elements, have a better language awareness, improve their reading and listening comprehension, and are more creative when making a composition. However, little specific work has been done in this regard in Colombia, especially with adolescents. This action research study explores the affordances of a corpus in English as a foreign language writing of fourteen students at the high school level. Surveys, teacher's journals, and classroom artifacts were used to collect data. Findings show that the corpus contributed positively to L2 writing in two ways. The participants could self-correct their mistakes associated with the use of collocations and prepositions, and the tool amplified participants' autonomy, decision-making, and data analysis skills. Although a corpus represents an alternative for error correction processes, it requires a well-structured instructional design process to deal with difficulties related to using commands derived from a corpus-based strategy.