Generalised access to the Internet and globalisation has led to increased demand for translation services and a resurgence in the use of machine translation (MT) systems. MT post-editing or the correction of MT output to an acceptable standard is known to be one of the ways to face the huge demand on multilingual communication. Given that the use of translation and MT post-editing are increasing the demand for language-skilled professionals, in this article we aim at evaluating the use of MT post-editing in the foreign language class. For this purpose we make use of computer-aided error analysis (CEA) to extract patterns of error found in translation and MT post-editing into the foreign language. This methodology will provide some insights as to the main difficulties found by the students in post-editing into the foreign language and about the suitability of using raw MT output as input for foreign language written production. Thus, a comparative analysis of error frequency is performed on the results of a group of advanced students of Spanish doing post-editing as compared to another group doing translation in order to gauge the level of difficulty of MT post-editing as opposed to translation into the foreign language. (Contains 1 figure, 6 tables and 3 notes.)