How to Make It
Separate kohlrabi leaves from bulbs; peel bulbs, and set aside. Bring a large pot of water to a boil over high. Boil kohlrabi leaves until bright green and tender, about 3 minutes. Transfer leaves from water to a rimmed baking sheet, allowing excess water to drip off.
Chop half of the red onion, and place in a large bowl. Add ground beef, rice, oregano, garlic, 3/4 teaspoon of the salt, and 1/2 teaspoon of the pepper to bowl with red onion. Stir to combine, being careful not to overwork mixture; set aside.
Place 2 kohlrabi leaves flat in bottom of a 9 1/2-inch Dutch oven or heavy-bottom straight-sided skillet. Place remaining leaves on a cutting board; trim into 20 (4-inch square) pieces. Working one at a time, spoon about 1 tablespoon of beef mixture into 1 leaf piece. Roll leaf burrito-style around beef mixture (fold sides over mixture, then start from bottom and roll up). Repeat with remaining leaves and beef mixture. Place rolled dolmades into leaf-lined Dutch oven. Pour chicken broth over dolmades. Cover, and cook over medium-high until rice is cooked through and leaves are tender, about 45 minutes.
Meanwhile, core kohlrabi bulbs and discard tough centers. Thinly slice bulbs into matchsticks, and place in a medium bowl. Thinly slice remaining half red onion, and place in bowl with kohlrabi. Add tomatoes, cucumber, feta, olive oil, vinegar, and remaining 3/8 teaspoon salt and 1/2 teaspoon pepper. Toss to combine. Serve cooked dolmades with slaw and lemon wedges.