Mix Chili’s® Peppered Bacon Burger Mix-In Sauce with the ground beef until evenly combined. Form into four burger patties.
Grill and occasionally flip until the burgers are cooked thoroughly (160º F minimum internal temperature).
While burgers are grilling, prepare the yogurt sauce by combining the Greek yogurt, feta cheese and garlic.
Cut off ends of cucumber with a knife. Using a vegetable peeler, mandoline, or knife, carefully slice cucumber vertically into thin ribbons. Alternatively, slice cucumber horizontally or chop finely into small cubes.
Top patties with yogurt sauce, spinach or arugula, and cucumber slices. Serve on toasted buns.