Preheat oven to 400 degrees F (200 degrees C). Lightly grease a medium baking sheet.
In a large bowl, mix spinach, cottage cheese, Parmesan cheese, Monterey Jack cheese, egg, and onion. Spread half the mixture over each phyllo pastry sheet. Roll pastry sheets jelly-roll fashion, pinch ends to seal, and arrange on the prepared baking sheet.
Make a few small slits in the top of each rolled pastry sheet. Bake 40 minutes in the preheated oven, until golden brown.
