1. Quarter cucumber lengthwise, then slice 1/2 in. thick. Toss cucumber, peppers, tomatoes, and onion in a large bowl; set aside.
2. Whisk together 1/4 tsp. salt, the orange zest, orange juice, lemon juice, and oil in a small bowl. Set dressing aside.
3. Brown bacon in a large nonstick frying pan over medium heat until golden, turning once, 4 minutes. Cut into 1/4-in. strips.
4. Put eggs in a small saucepan, cover with water, and bring to a boil. Turn off heat, cover pan, and let sit 3 minutes for soft-cooked. Crack eggs all over on counter, transfer to a bowl of ice water, and let cool 2 to 3 minutes. Peel and halve lengthwise.
5. Meanwhile, tear bread into 1/2- to 1-in. pieces. Add to vegetables along with bacon and dressing, and toss until evenly coated.
6. Divide salad among 4 shallow bowls and top each with 2 egg halves. Season to taste with pepper and more salt.
Make ahead: Up to 2 days, chop vegetables and cook eggs (let sit 10 minutes).