Rinse the brown basmati rice under cold water until the water runs clear.
In a small saucepan, combine the rice and chicken broth; bring to a boil, then reduce heat to low, cover, and simmer for 40 minutes until the liquid is fully absorbed.
While the rice is cooking, dice the chicken breast into bite-sized cubes.
Season the chicken cubes evenly with sea salt, black pepper, and dried oregano.
Heat the olive oil in a large skillet over medium-high heat.
Add the chicken to the skillet and sear until golden brown and cooked through, approximately 6 to 8 minutes, then remove the chicken and set aside.
In the same skillet, add the diced onion and bell pepper, sautéing for 5 minutes until the vegetables are softened and slightly caramelized.
Stir in the minced garlic and cook for 1 minute until fragrant.
Add the cooked brown basmati rice and the seared chicken back into the skillet, tossing all ingredients together to combine.
Fold in the baby spinach and cook for 1 minute until just wilted, then finish with a fresh squeeze of lemon juice before serving.