Pour 2 tablespoons of the olive oil into a 3-quart saucepan over medium heat, add the onion and cook, stirring constantly, just until the it begins to turn golden, about 2-3 minutes.
Add the garlic and oregano and continue cooking until the garlic is fragrant, about 1 minute.
Add the stock, chickpeas, lemon zest and bay leaf to the saucepan, increase the heat to high and bring to a boil. Immediately reduce the heat to low, cover and simmer until the chickpeas are creamy but not disintegrating, about 30 minutes.
Stir the salt, pepper, lemon juice and remaining 2 tablespoons of olive oil into the soup. Taste and add more salt and pepper if desired. Serve immediately with a drizzle of olive oil on top.