1Place shredded cucumber in clean dish towel; squeeze to remove any excess liquid. In small bowl, mix cucumber and remaining sauce ingredients. Cover; refrigerate until serving time.
2Heat gas or charcoal grill. In large bowl, mix all burger ingredients except buns, tomatoes and lettuce. Shape into 8 patties, 1/4 inch thick. Place patties on grill over medium heat. Cover grill; cook 5 to 8 minutes, turning once, until meat thermometer inserted in center of patties reads 160°F.
3Spoon 2 tablespoons sauce on bottom half of each bun. Top with burger, tomato and lettuce. Cover with top halves of buns.