For easy clean-up, place a cooking bag in your slow cooker.

In a large bowl, mix together the chopped chuck, oregano, onion powder, lemon pepper, and salt. Form the beef into 4 patties and place in a single layer in the slow cooker.

Cover the burgers with the barbecue sauce, and cook on low for 3-4 hours, until they reach an internal temperature of 160°F.

When the burgers are almost done, melt the butter in a large saucepan over medium high heat, then add the onions and cook until caramelized.

To serve, place burger on bun, top with cheese, lettuce and onions. Drizzle some extra barbecue sauce over burger if desired.