Heat 2 tablespoons of olive oil in a medium pot over medium-high heat. Add the onion, green pepper, and mushrooms. Cook, stirring occasionally for about 8 minutes, until the vegetables soften and the onions become lightly golden.
Add the garlic and cook 1 minute, stirring constantly, until fragrant.
Add the rice on top of the vegetables along with 1 teaspoon oregano, 1 teaspoon turmeric, ½ teaspoon salt, and ½ teaspoon black pepper. Cook, stirring frequently, for 5 minutes, until the rice is lightly toasted and coated in the spices.
Meanwhile, in a small bowl, combine the shrimp with the remaining 1 tablespoon olive oil, the remaining ½ teaspoon oregano, ½ teaspoon turmeric, ¼ teaspoon salt, and ¼ teaspoon black pepper.
Pour the water over the rice and bring to a boil. Once boiling, add the shrimp on top of the rice in an even layer. Cover with a tight-fitting lid, reduce the heat to low, and cook undisturbed for 15 minutes. Remove from the heat and let it sit, covered, for 5 minutes.
Fluff the rice gently with the shrimp and serve warm.