The aim of this research is to diagnose and help students overcome their problems through practice activities in English Language Education Departments in Turkey. This paper measures the perception of co-articulatory information in terms of consonant-to-consonant relations in the structure of vocabulary items and affixes of English. Thirty eight freshmen who are presently studying in the department of English language education at Hacettepe University are the participants, who were given a pretest on vocabulary items that include 25 questions, with five alternatives for the diagnosis of the secondary articulations in the words. Thereafter, a three-hour intense teaching and practicing process took place. After two weeks, the participants were given a posttest that included new vocabulary items not asked in the pretest. Results of data analysis revealed that co-articulation and secondary articulation connection in the creation of assimilations constituted a serious pronunciation problem due to consonantal and vowel assimilations for Turkish students of English Language Education. Results also indicated that the perception of assimilation is weak at the end of the pretest, but there is a remarkable development after the instruction on secondary articulation and coarticulation in relation to the perception of assimilation in connected speech in English utterances.