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Instructions
Combine sour cream, ranch dressing, and taco sauce in a bowl until smooth. Cover Southwest sauce; refrigerate for flavors to blend.
Preheat an outdoor grill for medium-high heat and lightly oil the grate.
Cook hamburger patties on the preheated grill for 5 minutes, seasoning with Worcestershire sauce. Flip patties and arrange tortillas on grill; reduce heat under tortillas to medium-low. Top tortillas with Cheddar cheese and Colby-Jack cheese. Continue cooking patties until cooked through, about 5 minutes. Cook tortillas until cheeses melt, 2 to 4 minutes. An instant-read thermometer inserted into patty centers should read at least 160 degrees F (70 degrees C).
Spread Southwest sauce onto 4 tortillas, cheese-sides up; top each with lettuce, picante sauce, and 1 patty. Top with remaining tortillas, cheese-sides down.