Place the spinach in a large bowl.
Add the zoodles and top with cucumber, tomatoes, red onion, and feta cheese.
Whisk (or shake in a jar) olive oil, lemon juice, oregano, salt, and pepper together until dressing is smooth.
Pour over zoodle mixture and toss to coat.
Allow flavors to marinate in the refrigerator for 10 to 15 minutes.