In this essay, the focus is on the grammatical development of four Swedish as a second language learners and how the former can be explained by using Manfred Pienemanns processability theory. In the study, three questions are posed. Firstly, on what levels of the processability theory are the participants processing morphology and syntactical structures? Secondly, how automated are the processing of morphology and syntactical structures? Lastly, how can processability theory be used to outline the grammatical development in relation to the participants’ formal education in Swedish and how long time they have been exposed to the second language? The empiric material is based upon two sets of semi-structured interviews with the participants in pairs. Furthermore, as I am reusing the material collected in a previous study, the participants have given their written consent for me to do so. The results of the study indicate that Pienemann’s theory can be used to outline the grammatical development of the four participants. The emergence criterion can be used to measure whether the participants has acquired a level of grammatical processing, in regard to PT. In three cases of four, the criteria of 50 and 80 percent in correctness is used to analyse the extent of the participants’ grammatical development.