Set up grill for two-zone cooking with one side of the grill with high heat and the other side with low heat if possible. Season the steaks on both sides with kosher salt or alternatively, steak seasoning of your choice.
Oil the grill grates or spray with cooking spray prior to placing the steaks on the hot side of the grill. Sear the first side of the steaks for a couple minutes or until nicely browned then flip the steak and sear the other side.
When both sides of the steak have nice color move the steaks to the side of the grill with lower heat. Continue to cook the steaks until they have reached the desired internal temperature when measured with an instant read thermometer inserted into the middle of the steak.
Steak Doneness: Rare= 120°F, Medium Rare=130°F, Medium=140°F, Medium Well=150°F, Well Done=160°F
Rest the meat for 5 minutes after removing from the grill then slice and assemble sandwiches on rolls with the red peppers, lettuce and horseradish sauce.