This study investigated the influence of regular structured writing about problem solving on college algebra students' locus of control, flexibility of articulation, and accuracy in responding to written problem tasks. The writing assignments, acronym PSOLVE, provided students a framework for expressing their thoughts about mathematical actions, processes, structures, and language. Given that augmenting traditional college algebra classes with the PSOLVE writing assignments resulted in statistically significantly higher scores on routine problems on the common posttest (p less than 0.05), we examined PSOLVE and non-PSOLVE students' written mathematical justifications in response to mildly non-routine short-answer items on the same posttest. PSOLVE students posttest explanations were clear and mathematically consistent. The PSOLVE writing assignment appears to be a useful support for growth of declarative and procedural knowledge as well as an effective conduit for the instructor to gain insight into students' thinking. We discuss potential benefits of the PSOLVE augmentation for the development of research and practice in college mathematics teaching.