Mediterranean Tuna Salad

1,  15- to 19-ounce can beans, such as chickpeas, black-eyed peas or kidney beans, rinsed

2,  5- to 6-ounce cans water-packed chunk light tuna, drained and flaked

1 large red bell pepper, finely diced

½ cup finely chopped red onion

½ cup chopped fresh parsley, divided

4 teaspoons capers, rinsed

1½ teaspoons finely chopped fresh rosemary

½ cup lemon juice, divided

4 tablespoons extra-virgin olive oil, divided

Freshly ground pepper, to taste

¼ teaspoon salt

8 cups mixed salad greens