Despite some school efforts to offer students the best second language learning, English language lessons are often taught with an overuse of the mother tongue. Hence, an action research project was conducted in order to discover how to adapt some features of the Sheltered Instruction Observation Protocol (SIOP) component: Lesson delivery, for the teaching of English in sixth grade at a public school in Bogotá, Colombia. Data collection included observation checklists, field notes, surveys and artifacts. The findings demonstrated that the overuse of Spanish--the students' mother tongue--was reduced when in addition to implementing the lesson delivery component, the teacher developed vocabulary activities. Finally, it was suggested that teachers have SIOP training for teaching content and to focus more on students needs.