Cut each pita bread in 8 slices. Put slices on a baking sheet and cook under the preheated grill 1 to 2 minutes or until crispy. In a large bowl, with a whisk, mix lemon juice, oil, cumin, salt and cayenne pepper. Add chickpeas, tomatoes, cucumber, bell pepper, green onions, nuts and mint. Stir.
Put 2 lettuce leaves on each bowl (4 bowls) and distribute chickpea salad. Sprinkle with feta cheese. Serve with pita slices.