1. Divide beef into 2 equal portions, shaping each into a 1/2-inch-thick patty. Rub olive oil on both sides of patties.
2. Heat a nonstick skillet or grill pan over medium heat. Place patties in pan; cook 6 minutes on each side, or until a meat thermometer inserted into middle of burger registers 160ï¿½.
3. Combine green beans, white beans, kidney beans, carrot, bell pepper, and vinaigrette in a bowl; toss gently.
4. Serve burgers and a few lettuce leaves on whole-grain buns with bean salad on the side.