01 - 
                Whisk together olive oil, lemon juice, chopped garlic, oregano, salt, and pepper in a small bowl.
              
              
              
                02 - 
                Place diced chicken in a large resealable bag or bowl, pour marinade over, and toss to coat evenly. Seal and refrigerate for 45 minutes to 1 hour.
              
              
              
                03 - 
                Thread marinated chicken pieces onto skewers, leaving small spaces. If using wooden skewers, soak in water for 30 minutes prior to use.
              
              
              
                04 - 
                Preheat grill to medium-high heat, oil grates to prevent sticking. Grill skewers for 8–10 minutes, turning occasionally, until internal temperature reaches 163°F. Optionally baste once with leftover marinade. Let rest 5 minutes before serving.
              
              
              
                05 - 
                Preheat oven to 350°F. Arrange chicken pieces on a greased baking sheet and bake 5–7 minutes per side until internal temperature reaches 163°F. Rest 5 minutes before serving.
              
              
              
                06 - 
                Warm pita bread on grill or in oven. Fill with grilled chicken, sliced tomatoes, red onion, tzatziki sauce, and a drizzle of fresh lemon juice. Serve immediately.