Trim any fat from the edges of the sirloin. Cut against the grain into very thin slices.
In a medium bowl, mix together worcestershire, soy sauce, brown sugar, garlic powder, onion powder, red pepper and peppercorn.
Place sirloin slices in soy sauce mixture. Cover and refrigerate overnight. Or for at least 1 hour, if overnight is not possible.
Preheat to 300 degrees F. Place sirloin slices atop the GoodCook Crispy Baking pan. Arrange in a single layer, with none of the slices touching.
Transfer to oven and immediately turn the temperature down to 275 degrees. Bake for 10 minutes, then turn oven to lowest temperature (170-175F) and bake for 3-4 hours, until desired texture is reached. Store in an airtight container for up to 2 weeks.