Heat oil in medium saucepan over medium-high heat. Add onions; cook until soft and translucent, about 7 minutes. Stir in jalapeño pepper, garlic and cumin; cook until fragrant, about 30 seconds more. Add the chicken and drained beans to saucepan and cook, stirring constantly, about 5 minutes.
To assemble burritos, mound rice, chicken and bean mixture, cheese, chopped scallions and cilantro on one side of tortilla. Roll up tortilla into burrito shape. Place burrito, seam-side down on serving plate or platter. Repeat with remaining ingredients.
Serve burritos with salsa, sour cream and guacamole, if desired.
For a fun twist, skip the tortilla, and just make your burrito in a bowl!