In the area of foreign language reading research not enough is known of the extent to which foreign language readers can comprehend the texts in which textual signals are explicitly or implicitly marked, and in which the discourse mode varies from one type to another. This research investigates how Iranian undergraduate readers of English approach narrative, expository, and argumentative text types in which propositional relations have been explicitly or implicitly marked through connectors. Participants read passages of each text type in both their explicit and implicit versions. The readability, length, average word frequency, and learner level which are hypothesized to have affected the results of the previous studies were controlled. The results demonstrate significant differences between learner level, and the explicit and implicit versions. The results confirm the contributory effect of these markers in comprehension. Therefore, language teachers, testers, and materials developers need to further consider the relationship between textual signals and text types in devising appropriate materials and techniques to improve foreign language learners’ reading comprehension.