Preheat the oven to 350 degrees F. Line a baking sheet with aluminum foil. Season the chicken breasts on both sides with salt and pepper.
Place into the oven and bake at 350 degrees F. for 30 to 40 minutes or until the chicken is fully cooked (the internal temperature has reached 165 degrees F.).
Remove the chicken and allow it to cool.
Chop the chicken breast into chunks or strips and in a medium bowl toss the cooked chicken with about ½ cup of the BBQ sauce.
Slice the French bread in half lengthwise. Spread a layer of the BBQ sauce onto the top of the cut sides of the bread. Top with a layer of mozzarella cheese. Top with red onions and chicken.
Place the French bread onto a baking a large baking sheet.
Place into the oven on the center oven rack and bake for 10-15 minutes or until the cheese has melted and started to brown.