This study explored writing processes in two languages (L1-Swedish and L2-English) and in two text types (argumentative and narrative) of 158 upper-secondary students by analysing keystroke logging data. The main aim of this study was to identify effective writing processes of argumentative and narrative tasks in L1 and L2. First, results of the mixed effects model analysis showed that students' typical writing processes displayed differences in timing, higher and lower order pauses, production speed, and revision depending on the language in which they wrote and the type of text they wrote. Secondly, using regression model analyses we explored which writing process patterns were positively related to text quality. By combining a reduced set of process measures, we identified effective writing process patterns. These patterns explained a rather substantial part of the variance in text quality, more precisely, between 56.1 % and 69.3 %. This study contributes to the current field of writing process studies by expanding our knowledge of typical and effective writing processes in argumentative and narrative writing in upper-secondary students' L1 and L2. These insights can be used to further shape writing education to support students’ writing across languages and text types.