Mix together yogurt, cucumber, garlic, and lemon juice. Spread evenly on the bottom of a pie dish or 9x9 baking dish
Add oil from the sun-dried tomatoes to a pan and bring to medium heat. add chickpeas, green onion, and garlic powder, mashing the chickpeas as you stir. Cook for about 5 minutes and during the last minute, add the sun-dried tomatoes. Let cool.
Combine red pepper, spinach, and feta. Top yogurt mixture with chickpea mixture, then top with feta mixture. This dip can be made 24 hours in advance.
Preheat oven to 375 degrees.
With a pastry brush, coat each side of the pitas evenly with olive oil. Cut each pita into eight triangles and transfer to baking sheet.
Sprinkle with oregano and garlic powder. Bake for about 10 minutes or until pita slices are golden around the edges. Remove from oven and sprinkle with salt.