Combine first 6 ingredients in a small bowl. Stir well. Cover and chill.
Coat a large nonstick skillet with cooking spray or a little olive oil. Add lamb and onion. Cook over medium-high heat, stirring occasionally, 6-7 minutes or until lamb is done. Remove from heat. Stir in Greek seasoning.
Divide lamb mixture evenly among 4 tortilla. Topp with cucumber sauce, tomato, and spinach. Roll up tortillas.