Clean the grill grates and spray with nonstick cooking spray. Line a baking sheet or tray.
Add the ground beef, sausage, Worcestershire sauce, onion, garlic, rosemary, salt, and pepper to a large bowl. Combine thoroughly. Make sure both types of meat and all seasonings are completely incorporated throughout the mixture.
Divide the meat mixture into 8 equal parts and shape each into 3/4 inch thick patties.
Place the patties on the prepared baking sheet and use your thumb to create an indent in the middle to keep them from puffing up while cooking.
Cook patties on the grill over direct, high heat for 8-10 minutes. Final cooking time will vary.
When the burgers seem to be about 2-3 minutes away from being done, move them to indirect heat and top with the blue cheese. Close the grill's lid and allow the cheese to melt completely.
Serve on toasted buns and topped with sliced avocado and your other preferred toppings (bacon, lettuce, tomato, etc.) and condiments.