Add the leftover roast and onions to a food processer and pulse 10 to 12 times. Additional processing will result in a finer texture.
Place the ground mixture into a mixing bowl and add the salad dressing and relish.
Stir to combine.
Taste the beef salad and add salt and pepper to taste.
Serve as a sandwich filling or cracker spread.
Notes
Store leftovers in the refrigerator for up to 3 days.
Mayonnaise with additional pickle relish or sweet pickle juice can be used as a substitute for Miracle Whip.
1 sweet pickle or 2 midget sweet pickles finely minced plus 1 teaspoon of pickle juice can be used as a substitute for sweet pickle relish.
Serve as the filling for a roast beef salad sandwich or an appetizer cracker spread.