In a medium bowl, toss the shrimp with 1 tablespoon of olive oil, 2 cloves of minced garlic, 1/2 teaspoon of oregano, and a pinch of salt and pepper.
Heat a large skillet over medium-high heat and add the seasoned shrimp.
Sauté the shrimp for 2 to 3 minutes per side until pink and opaque throughout; remove from the heat and set aside to cool slightly.
In a small jar or bowl, whisk together the remaining 3 tablespoons of olive oil, lemon juice, red wine vinegar, remaining minced garlic, remaining oregano, and remaining salt and pepper to create the dressing.
In a large serving bowl, combine the spinach or romaine, cucumber, tomatoes, red onion, and Kalamata olives.
Top the salad with the cooked shrimp and crumbled feta cheese.
Drizzle the lemon-herb dressing over the salad and toss gently to combine.
Serve immediately as a high-protein, keto-friendly main dish.