The study aimed to analyze the effects on reading of an early oral and written language intervention program for Spanish children at risk of learning difficulties. The goal of this classroom-based program was to prioritize a systematic approach to reading and writing and to foster phonological knowledge and the development of oral language (phonology, semantics, morphology, and syntax) within the Spanish school curriculum. The sample comprised 56 students at risk of learning difficulties. The repeated-measures longitudinal design involved four assessment and three intervention points over a period of 3 years, considering two study groups (instruction vs. no instruction) and two variables (reading accuracy and reading comprehension). Children were assessed between the ages of 5 and 7 years. The instruction group scored higher on both reading accuracy and reading comprehension at all assessment points. Overall, the results demonstrate that this early intervention program for oral and written language is an effective way of improving the reading performance of children at risk of learning difficulties.