Pound the chicken breasts so that they flat (this will also help make the chicken very tender). Season with salt and pepper.
Cook the chicken over an outdoor grill over medium high heat; 6-7 minutes per side or until fully cooked. If you don't have an outdoor grill, you could easily cook it over an indoor grill or in a skillet on the stove top that has been sprayed with cooking spray.
After the chicken is finished cooking, transfer the chicken breasts to a large baking sheet covered in aluminum foil. Spread 2-3 tablespoons of barbecue sauce over each chicken breast. Top each chicken breast with 2 slices of bacon and and a handful of the shredded cheese mix. Place the baking sheet in an oven broiler (or microwave long enough to melt the cheese). Top with diced tomatoes and green onions. Serve immediately.
Notes
One of the reasons we like to pound the chicken before we cook on the grill is to minimize the amount of time it takes to cook the chicken. The other reason is because it causes the chicken to be wonderfully tender.