In a large skillet over medium heat, add 1 pound of ground beef and cook for about 5–7 minutes, stirring occasionally, until browned. Season with salt, pepper, and oregano to taste. Once the beef is nearly cooked, add 1 cup of sliced mushrooms and continue sautéing for an additional 4–5 minutes, or until the mushrooms are tender and everything is well combined.

While the beef and mushrooms cook, mix together 1 cup of Greek yogurt, 1 diced cucumber, 2 minced garlic cloves, and 1 tablespoon of fresh dill in a bowl. Squeeze in the juice of half a lemon and stir until well combined. Allow the tzatziki sauce to chill in the refrigerator for about 10 minutes.

Warm the pita bread either in a dry skillet over medium heat for about 1–2 minutes on each side or in a preheated oven at 350°F for 5 minutes.

Take a warm pita and carefully open it up to create a pocket. Spoon in the beef and mushroom mixture, packing it generously, and then drizzle a few spoonfuls of the fresh tzatziki sauce on top.

Arrange the pita pockets on a platter or serve individually, enjoying their vibrant flavors and textures.