Grind together bologna, pimiento cheese, onion, and pickles.
Add salad dressing, green pepper, and mustard.
Spread bread slices with margarine.
Spread each of 6 slices of rye bread with 1/4 cup filling; top with 6 slices bread.
Arrange lettuce and sliced tomatoes atop.
Cover sandwiches with remaining 6 slices of bread, buttered side down.