Mix kosher salt, black pepper, and seasoned salt together in a small bowl to make seasoning mixture.

Shape ground chuck into four 6-inch patties that are 3/4-inch thick. Press your thumb into the center of each patty to make an indentation. Brush 1/2 teaspoon oil over each side. Sprinkle 1/2 teaspoon seasoning mixture over each side.

Place seasoned patties on a plate lined with waxed paper and freeze until firm, about 15 minutes.

Fill a barbeque starter chimney with lump charcoal and ignite in an outdoor briquette barbecue grill; heat until charcoal turns white. Spread charcoal evenly on lower grate. Add upper grate, cover grill, and let heat for 5 minutes. Lightly oil the grate.

Grill patties, covered, until browned, about 5 minutes. Flip and cook until second side is browned, about 4 minutes. Place 2 slices Monterey Jack cheese over each patty; cook until melted, about 1 minute. Transfer patties to a plate and tent with aluminum foil.

Brush 1 tablespoon melted butter over insides of each roll. Place roll halves buttered-side down on the grill; toast until golden, 30 seconds to 1 minute. Transfer to a flat work surface.

Top the bottom half of each roll with 1/4 of the avocados, 2 lettuce leaves, 1 tomato slice, 1/4 of the red onion slices, and 3 slices of bacon.

Whisk mayonnaise and horseradish together in a bowl until smooth. Spread a thin layer of mayonnaise mixture on each burger patty and place over bacon slices. Cover with top halves of rolls.