Soak the potato wedges in ice water for 30 minutes.
Preheat oven to 425F. Move the rack to the middle position.
Add the garlic powder, oregano, paprika, onion powder, salt & pepper, lemon juice, and olive oil to a small bowl.
Dry the potato wedges off (I use paper towel) and add them to a large Ziploc. Pour the seasoning mixture over them then toss until they’re evenly coated. Arrange them in an even layer on a baking sheet.
Bake for 25-30 minutes, flipping halfway through. Meanwhile, prepare the tzatziki.
Top them with the tzatziki (or put some in a container for dipping), feta, red onions, and parsley. Squeeze extra lemon on if desired.