1) Place rice and chicken in a saucepot and bring to a boil. Reduce heat and cook rice, covered, until tender and all the liquid is absorbed, 30 to 35 minutes. Remove from heat, uncover, and fluff with a fork.
2) Heat the oil in a large saute pan over medium-high heat. Add onions and cook until onions are soft and translucent, about 5 minutes. Add garlic, oregano, celery, carrot, cumin and chili flakes and cook, stirring occasionally, until carrots are tender but not mushy, about 6 minutes. Stir in black beans and cook until just warmed through, about 1-2 minutes.
3) Combine onion-black bean mixture and hot rice in a serving bowl and toss to combine. Garnish with parsley.