Liberally spray the inside of a large crockpot with non-stick cooking spray, or use a disposable slow cooker liner for easy cleanup.

Pat the trimmed chicken breasts dry with paper towels. Season both sides with salt, pepper, garlic powder, and onion powder. Place them flat in the bottom of the crockpot in a single layer.

In a medium mixing bowl, whisk together the barbecue sauce, Italian dressing, light brown sugar, and Worcestershire sauce until fully combined and smooth.

Pour the sauce mixture evenly over the seasoned chicken breasts, making sure every piece is well coated. Place the lid on the crockpot.

Cook on HIGH for 2.5 to 3 hours or on LOW for 5 to 6 hours. Begin checking at the low end of the time range to avoid overcooking.

Check internal temperature with a meat thermometer. Chicken must reach 165 degrees F before serving.

Use two forks to shred the chicken directly in the crockpot so every strand absorbs the BBQ sauce. Serve immediately or keep on the warm setting for up to 1 hour.