Drain and rinse the 15-ounce can black beans and the 15-ounce can corn; combine them in a bowl and set aside.
In a small bowl, stir together the 1 1/2 cups plain Greek yogurt and 3 tablespoons salsa ranchera until smooth; set the sauce aside.
Place the cooked, diced chicken breasts and cooked, diced chicken thighs in a bowl. Season with salt, pepper, and taco seasoning; toss until evenly coated. (If you prefer warm chicken, reheat gently in the microwave or in a covered pan until just heated through.)
Confirm the large butternut squash is cooked and diced into bite-size pieces; if it is not already diced, cut it into bite-size pieces now.
Divide the 4 cups prepared quinoa (or rice/grain mix) evenly among your bowls or meal containers.
Evenly distribute the seasoned chicken, the diced butternut squash, and the bean/corn mixture over the quinoa in each bowl.
Spoon the yogurt–salsa ranchera sauce over each bowl or serve it on the side.
Taste and, if desired, adjust with additional salt, pepper, or taco seasoning.