Season the chicken breast with salt, pepper, and dried oregano. Heat a skillet over medium-high heat and add olive oil. Cook chicken for about 6-7 minutes per side until golden brown. Let rest for 10 minutes before slicing.

Rinse the lettuce under cold water and chop into bite-sized pieces. Slice the cucumbers and tomatoes into chunks and thinly slice the red onion.

In a large serving bowl, layer the chopped lettuce, cucumbers, tomatoes, red onion, and sliced chicken. Add Kalamata olives and crumble feta cheese on top.

In a jar, combine olive oil, red wine vinegar, minced garlic, sugar, salt, and pepper. Shake vigorously for about 30 seconds.

Drizzle the dressing over the salad and gently toss to coat. Serve immediately.