In a small bowl, combine first seven ingredients (olive oil through black pepper); stir with a whisk. Place shrimp and vegetables in two separate bowls, and divide marinade evenly into each one; toss to coat. Let stand 5 to 10 minutes.
Meanwhile, combine farro or rice in a saucepan with broth. Bring to a boil, reduce heat to low, and gently simmer, covered, until grains are tender and most liquid is absorbed. (This will take about 15 minutes for white rice, and up to 30 minutes for farro.)
Meanwhile, heat a large skillet coated in cooking spray (or lightly greased with oil) over medium-high. Once hot, add shrimp and cook 2 minutes per side, or until opaque. Transfer to a plate. (If your skillet isn't large enough to fit all shrimp in a single layer, cook in two batches.) Next, add vegetables to the same skillet and cook until tender, about 8 minutes.
Prepare Lemon-Garlic Yogurt by combining yogurt, garlic, lemon juice, and salt in a small bowl. Stir in 1 to 2 Tbsp. water to thin out to desired consistency.
Assemble bowls by dividing farro or rice evenly into each of 4 bowls. Scatter shrimp and vegetables overtop, and finish with a dollop of Lemon-Garlic Yogurt. If desired, garnish with sliced cherry tomatoes, olives, or fresh herbs. Finish with a drizzle of olive oil.