Heat a grill to medium-high. Clean and lightly oil hot grill.
Using food processor, pulse onion, garlic and chipotle until a smooth paste forms. In a large bowl, combine ground beef, chipotle paste, salt and pepper. Using your hands, mix until well combined.
Divide mixture into 6 equal portions. Between palms of hands, form each portion into a 4-by-1-inch oval patty. Insert an 8-inch skewer lengthwise into each patty. Grill, turning occasionally, until meat is browned and cooked through, 6 to 8 minutes.