Heat oil in a large straight-sided skillet over medium heat. Season chicken with 1 teaspoon salt and 1/4 teaspoon pepper. Cook, turning, until golden on all sides, about 10 minutes; transfer to a plate.
Add onion, garlic, 1 teaspoon salt, and 1/4 teaspoon pepper to skillet. Cook, stirring frequently, until onion is softened, 3 to 5 minutes.
Stir in rice, tomatoes, peppers, and 1 1/4 cups water; nestle chicken pieces in rice mixture. Bring to a boil; reduce heat. Cover, and simmer over medium-low heat until rice is tender, 55 to 60 minutes. If any liquid remains in skillet, remove lid and simmer until evaporated.
Sprinkle peas over contents of skillet; cover, and remove from heat. Set aside until peas are heated through, about 10 minutes. Serve with lemon wedges, if desired.
To save some time later, cover the brown rice with water in the morning, and let it soak all day; this will reduce the cooking time by about 20 minutes.