Preheat your Traeger Flatrock griddle in two zones to medium heat.
Arrange the bacon slices on one zone of the hot griddle and cook until just crisp.
Transfer the bacon to a paper towel lined plate and scrape off most of the bacon grease.
Remove the chicken from the marinade and place it on the section of the hot griddle where you just cooked the bacon.
While the chicken cooks, make the horseradish ranch sauce by mixing together the mayo, horseradish, ranch mix, buttermilk, hot sauce and parmesan. Taste and adjust seasoning to your preferences.
Assemble the rest of your ingredients-- slice the tomatoes, wash and cut the lettuce into big pieces, and slice the red onion on a big cutting board.
Slice the hoagie rolls in half, leaving the edge intact.
Brush the inside of the hoagie rolls with the remaining ½ teaspoon mayonnaise.
Flip the chicken and continue cooking until it reaches an internal temperature of 150*.
Add slices of the Cabot Vermont Sharp Cheddar cheese to the top of each chicken piece on the griddle.
Cover the chicken and cheese with a cooking dome or lid and continue cooking until the internal temperature reaches about 160* and the cheese is fully melted.
Allow the chicken to rest on a loosely tented plate for about 5 minutes.
Toast the hoagie roll until golden brown.
Put 3-4 chicken and cheese pieces on top of the vegetables on your cutting board.
Add a few slices of bacon and a few spoonfuls of the prepared sauce.
Using a cleaver, chop your ingredients until even bite-sized pieces have been achieved and the ingredients are combined.
Scoop the chopped chicken, cheese and vegetables into the prepared hoagie rolls.
Serve your Cheesy Chopped Bacon Chicken Ranch sandwiches while hot and enjoy!