Bring chicken broth and quinoa to a boil in a saucepan. Reduce heat to medium-low, cover, and simmer until quinoa is tender and water has been absorbed, 15 to 20 minutes.
Heat 1 tablespoon oil in a skillet; cook and stir chicken until no longer pink in the center, about 10 minutes.
Heat 1 tablespoon oil in a separate large skillet over medium heat; cook and stir onion, green bell pepper, and jalapeno pepper until tender, 5 to 10 minutes. Mix quinoa, chicken, black beans, salsa, tomato paste, garlic salt, cumin, chili powder, black pepper, and oregano into onion mixture; cook, stirring occasionally, until casserole is heated through and thickened, 5 to 10 minutes. Top casserole with sour cream and Cheddar cheese.
