Shrimp and grits are always a good idea—especially when they're served with kalamata olives and feta cheese and ready in 25 minutes.
Arrange a rack under the broiler; preheat to high. In a medium bowl, mix 3 tbsp. oil with the vinegar, garlic, 1 tsp. dried oregano, and 1/2 tsp. crushed red pepper; season the dressing with salt and pepper.
On a large rimmed baking sheet, toss the tomatoes, shrimp, and olives with the dressing. Broil until the tomatoes burst and are blistered in spots, about 10 minutes.
In a large bowl, toss the spinach with the remaining 1 tbsp. oil; season. Add the spinach to the baking sheet; toss with the shrimp and tomatoes. Broil, stirring halfway through cooking, until the spinach wilts and the shrimp are just opaque in the centers, about 3 minutes.
Divide the polenta among bowls. Top with the shrimp and vegetables. Drizzle with the juices from the baking sheet. Drizzle each bowl with a little oil. Top with the feta, remaining 1 tsp. dried oregano, and more crushed red pepper.