Spray crock pot with non-stick cooking spray or use a slow cooker liner.
Cut meat into thin strips, place in slow cooker. Add green pepper, onion, stock, garlic salt, pepper and dressing mix.
Cover and cook on low 7-8 hours, or high for 3-4 hours.
Spoon meat mixture onto toasted buns, top with cheese.
You can then put the sandwiches on a baking sheet and bake an additional few minutes to melt the cheese and toast the sandwich.
You can also serve with sliced sauteed mushrooms on top.