In a medium-size bowl, whisk together olive oil, vinegars, garlic, and oregano. Season with salt and pepper to taste and set dressing aside.
In a skillet over medium heat, warm 1 teaspoon of oil. Add onions and cook until translucent. Remove onions and set aside to cool. Return pan to the stove.

Season shrimp with salt and pepper. Add 1 teaspoon of oil to the pan and cook shrimp a few minutes on each side until cooked through; refrigerate until ready to serve.

In a large bowl, combine chopped onions, couscous, chickpeas, cucumber, tomatoes, olives, and artichokes; mix well. Toss in cubed feta and pour dressing over mixture. Refrigerate several hours, or overnight if possible.

To serve, toss chilled couscous salad and top with chilled shrimp.