Preheat oven to 375 degrees.
Roll out dough into a large 12x8 rectangle. Cut in half and then cut each half into 3 equal squares. (you will have 6 total squares to work with)
Evening distribute pepperoni, green bell peppers, red bell peppers, diced red onion, and mozzarella on one half of each square.
Fold over the unfilled half of the square to create a pocket and pinch the edges together so that all the filling is enclosed.
Place pockets on a parchment paper lined baking sheets.
Brush the top of each pizza pocket with egg mixture.
Bake for 20 minutes, until tops of pizza pockets are slightly browned and hard.
In the meantime, heat medium saucepan pan to medium high heat. Add olive oil and red onions. Saute until transparent, about 3-4 minutes.
Add garlic to pan, saute for 30 seconds. Add in crushed tomatoes, bring to a boil. Reduce to simmer for 5 minutes. Season with salt and pepper.
Serve pizza pockets with marinara sauce.