1. Heat oil in large nonstick skillet over medium-high heat. Sprinkle polenta with salt and pepper. Add to skillet and cook 3 minutes per side, until lightly browned and crisp. Transfer to plate; keep warm
2. Add beef to skillet. Cook 3 minutes, until no longer pink, drain. Add salsa and drained beans; cook 5 minutes more, until heated through.
3. Arrange 2 slices polenta on each of four serving plates. Divide and top with beef mixture. Garnish with lettuce, if desired. Makes 4 servings.