Mix oil, lemon juice, garlic, mint, oregano, salt and pepper together in a small bowl. Use a fork or small whisk to combine.
Place steak in slow cooker.
Pour dressing over the top and stir to combine.
Cook on high 5-6 hours or low 7-8 hours.
Stir cucumber, yogurt and mint together.
Serve meat in pita bread, topped with cucumber sauce.