Heat the oil in a medium skillet. Add the onion and sauté until golden.
Add the bell pepper and barbecue sauce, then stir in the chickpeas. Cook over medium heat until the sauce is reduced and envelopes the chickpeas and veggies nicely, about 8 minutes.
Distribute 1 to 2 pita halves to each plate, depending on appetites and what else is being served. Fill each pita half with some lettuce, sprouts, tomatoes, and optional avocado, followed by the chickpea mixture. Serve at once.