Place bacon in a large, deep skillet. Cook over medium high heat until evenly brown. Drain, crumble and set aside to cool.
Prepare the dressing by mixing together the mayonnaise, parsley, green onions, lemon juice, Worcestershire sauce, salt and pepper.
In a medium bowl, stir together the chicken breast, tomatoes and bacon. Pour dressing over chicken mixture and toss well to coat. Refrigerate until chilled; serve over lettuce leaves and garnish with avocado slices.