Place chicken in a skillet or saucepan and add salted water to cover. Bring to a simmer over medium heat. Cover, reduce heat to low and simmer gently until chicken is no longer pink inside, about 10 minutes. Transfer chicken and poaching liquid to a shallow dish. Cover and refrigerate, letting chicken cool in the liquid.
Meanwhile, cook bacon in a skillet over medium heat until crisp, turning occasionally, about 7 minutes. Drain on paper towels and coarsely crumble.
Cut cooled chicken into 1/2-inch dice.
Toss lettuce in a large bowl with 1/3 cup dressing. Divide among 4 plates. Arrange chicken, bacon and tomatoes over lettuce and drizzle with remaining 1/3 cup dressing. Serve immediately.