Pulse chickpeas in a food processor until it is a mix of finely and coarsely chopped, about 15 pulses. Turn into a medium bowl; Mix in onion, celery, olive oil, olives, lemon juice, and oregano. Taste and adjust seasonings, including salt and pepper to taste. Let stand a few minutes for moisture to absorb. Serve. (Can be refrigerated in a covered container for a couple of days.)