The current study focused on developing essay writing skills and tried to overcome some problems that face Egyptian EFL prospective teachers (EFL-PTs) at the Faculty of Specific Education through their essay writing. The basic assumptions behind the research were to find out the impact of collaborative problem solving (CPS) strategy on developing EFL-PTs' essay writing skills. The goal was to collect a sample of EFL-PTs’ writing working collaboratively to solve different problems through essay writing (Treatment group, n=100) and then compare them with another writing group working individually (Non-treatment group, n=100). An essay writing test was developed, and then administered to measure how far essay writing skills of the treatment group developed after the intervention with the CPS strategy. It was found that the treatment group students who worked collaboratively significantly outscored the non-treatment group students who worked individually. Discussion of these findings is presented.