In a large bowl, mix the ground beef, oregano, onion powder, lemon pepper, and salt. Divide the mixture and form into 4 patties.
1 pound ground beef, ½ tablespoon oregano, 1 tablespoon onion powder, 1 teaspoon lemon pepper, 1 tablespoon salt
Spray the bottom of the slow cooker with non-stick cooking spray. Place the burgers in the bottom of the crock, in a single layer.
Cover the burgers with the barbecue sauce, and cook on low for 3-4 hours, until they reach an internal temperature of 160 degrees F.
2 cups barbecue sauce, plus extra for serving
When the burgers are almost done, slice the onion into rings.
1 onion, medium to large
Melt the butter in a large saucepan over medium high heat, then add the onions.
1 tablespoon butter
Toss the onions to coat with the butter, then allow them to cook, stirring frequently, until they become browned and caramelized.
Build your burgers with buns, cheese, and lettuce as desired. Drizzle a little extra barbecue sauce over the burger, then pile on some of the caramelized onions.
4 cheese slices, hamburger buns, lettuce leaves
If you need to layer your burgers to fit them, it may help to cover each layer with some sauce and even some onion strips to keep them from sticking to each other. Also, try not to lay the patties directly on top of each other. If you can stagger them, that will help also.
Start checking your burgers at the 3 hour mark until you know how fast they will cook in your particular slow cooker.
If you are cooking more than 4 burgers at a time, you may need to adjust the cooking time.
Use a slow cooker liner instead of using non-stick cooking spray to avoid sticking and make clean-up a snap!