Bring a medium saucepan of water to a boil. Stir in the rice, and simmer for 20 minutes. Transfer to a strainer and rinse under cold water until cool. Transfer to a large bowl.

Heat 1 teaspoon of the olive oil in a small pan over medium heat. Add the chopped onion and saute for 2 - 3 minutes. cook until translucent, 2 to 3 minutes. Add to the rice along with the mint, lemon zest, parsley, salt, lemon juice, and remaining 2 teaspoons of olive oil. Set aside (can be done earlier in the day)

Place the shrimp, 2 tablespoons of olive oil, garlic, 1/2 teaspoon of salt and black pepper in a large ziploc bag. Smush the bag to coat the shrimp and refrigerate for 30 minutes (or earlier that day).

Place the sliced onion in a small bowl and pour the lemon juice over - stir to coat the onion and set aside for at least 30 minutes.

Pre-heat the oven to broil and line a baking sheet with foil. Thread the shrimp onto metal skewers and place in a single layer on the baking sheet. Broil, turning once, till shrimp are cooked through - about 3 minutes per side. Remove from the oven and set aside.

Drain the lemon juice into a small bowl and set the onion aside. Add the oregano, remaining 1/2 teaspoon of salt and black pepper and whisk till combined. Continue whisking and slowly pour in the remaining 1/2 cup of olive oil. Whisk till emulsified (can do ahead - transfer to a covered jar and shake before using - keep in the fridge till ready to serve). Place the lettuce, tomatoes and cucumbers in a large serving plate or bowl and toss to combine.

To serve, place the rice on dinner plates and add the salad alongside. Remove the shrimp from the skewers and place on top of the salad. Garnish with the red onion and feta, passing the dressing separately.