Heat 1 tablespoon olive oil in a large skillet over medium heat until the oil shimmers.

Add 1/4 cup minced red onion and cook, stirring occasionally, until the onion is translucent, about 3–4 minutes.

Add 2 cloves minced garlic and cook, stirring, about 30–60 seconds, until fragrant.

Increase heat to medium-high and add 2 cups cooked brown rice. Break up any clumps with a spatula and stir to combine; cook until the rice is heated through, about 5 minutes.

Stir in 2 roma tomatoes, diced small, and 2 cups fresh baby spinach. Cook, stirring often, until the spinach is wilted and the tomatoes are warmed, about 2–3 minutes.

Remove the skillet from the heat and gently fold in 1/2 cup fat-free feta cheese until evenly distributed.

Serve hot.