Peer grading and peer feedback often fail, especially in larger classes, because they aren't set up properly. Check out this well-organized resource from Washington University in St. Louis.
Get your students writing more often in your discipline. It improves depth of learning. Here are several examples of low-stakes writing assignments for students.
A collection of excellent, research based advice on teaching writing. Examples: "Using Writing in Large Classes," "Tips on Grading: Using Rubrics," "Managing the Paper Load," and "Peer Review."