Heat olive oil in a skillet over medium heat and sauté chopped onion and minced garlic until softened.
Add ground beef, breaking it apart, and cook until browned and fully cooked.
Stir in ground cumin, paprika, oregano, salt, and pepper, cooking for 2 more minutes to blend flavors.
Remove beef mixture from heat.
Warm pita pockets in a toaster or oven.
Cut each pita pocket in half carefully to create pockets for filling.
Fill each pita half with the cooked beef mixture.
Top with diced cucumber, tomatoes, red onion, and chopped parsley.
Drizzle tzatziki sauce on top before serving.