Lightly coat the inside of your slow cooker with nonstick cooking spray or use a slow cooker liner.
Season the chicken breasts with garlic powder, onion powder, salt, and black pepper. Arrange them in the bottom of the Crockpot.
In a bowl, whisk together the BBQ sauce, Italian dressing, brown sugar, and Worcestershire sauce until combined.
Pour the BBQ sauce mixture evenly over the chicken and cover with the lid.
2½–3 hours on HIGH or 5–6 hours on LOW
Cook on HIGH for approximately 2½–3 hours or LOW for 5–6 hours.
Check the thickest part of the chicken with an instant-read thermometer. It should reach an internal temperature of 165°F (74°C).
Once cooked, shred the chicken directly in the Crockpot using two forks.
Toss the shredded chicken thoroughly with the BBQ sauce and cooking juices. Let it sit briefly in the warm sauce before serving.
Serve on toasted buns for BBQ chicken sandwiches, or use the chicken in tacos, rice bowls, baked potatoes, salads, nachos, or wraps.