Metacognitive skills are important for text comprehension, especially at university where most learning processes are unsupervised, and students rely on self-control and regulation when reading for comprehension. In today's universities, English as L2 has become the vehicle language for teaching and learning. However, some studies have concluded that university students who read English as L2 have inadequate metacognitive monitoring skills. Higher level processing skills, such as comprehension monitoring, are difficult to study and then improve. The main goal of the present study was to analyze the mental processing of readers when they monitored expository texts in English as L2 considering their English proficiency. Mental processing was related to readers' behavior when performing a reading task by using a set of variables guided by a psychological mechanism proposed for inconsistency detection. A total of 169 university students participated. The task was modeled on the error detection paradigm, which involved assessing the comprehensibility of scientific texts in English and reporting comprehension difficulties encountered. A special software was used to collect detailed data online about the readers' text processing and written reports. The results confirmed the set of processing variables and the theory-based predictions.