In a medium bowl, whisk together 1 Tbsp. oil, cumin and 1/4 tsp. salt. Add chickpeas, stirring to coat. In a medium nonstick skillet, cook chickpea mixture over medium-high heat, stirring occasionally, until chickpeas are golden brown and slightly crisp, 4 to 5 minutes. Add garlic and cook, stirring, until golden and fragrant, 30 seconds. Transfer to a plate.
In a large bowl, whisk together vinegar, remaining 2 Tbsp. oil, oregano and 1/4 tsp. each salt and pepper. Add romaine, cucumber, onion, chickpeas, olives and feta, if desired. Toss until well coated and serve.