Place zucchini, yellow squash, and onion in a large bowl. Add olive oil, lemon pepper seasoning, and seasoned salt. Toss to coat until evenly combined.
Preheat an air fryer to 400 degrees F (200 degrees C) for 5 minutes.
Place zucchini mixture in the basket of the air fryer making sure to not overcrowd (you may need to do this in two batches depending on the size of your air fryer).
Cook for 8 minutes. Shake basket and cook until vegetables are soft, about 8 minutes more.