Clean and slice onion and peppers. Preheat oven to 350 degrees. In a large sized frying pan, add olive oil, sliced onion, sliced red pepper and sliced yellow pepper. Cook over med/high heat for approx. 20 minutes turning every 5 minutes to cook through until peppers are soft.
While the peppers and onions are cooking, toast 2 pitas at a time in your toaster and lay the toasted pitas on a cookie sheet. Spread the hummus on each of the toasted pitas using approx. 2 tablespoons of hummus per pita.
Top each pita with a generous portion of the cooked peppers and onions. Add desired amount of mozzarella cheese on top of each.
Place cookie sheet in preheated oven for approx. 5 minutes until cheese is melted.