In a medium saucepan, prepare the instant brown rice according to package instructions. Typically, this involves boiling water, adding the rice, and letting it sit covered until fluffy (about 5 minutes).
In a skillet, heat olive oil over medium heat. Add the black beans and corn, cooking until warmed through (about 3-5 minutes).
Stir in the diced tomatoes and taco seasoning, combining thoroughly. Let it simmer for another 2-3 minutes to infuse the flavors. Adjust seasoning with salt and pepper, and add lime juice.
In each serving bowl, add a base of fluffy rice. Top with the warm black bean and corn mixture, followed by diced avocado, shredded cheddar cheese, and a sprinkle of fresh cilantro if desired.
Garnish with lime wedges on the side for squeezing over the bowls right before enjoying.
Notes
Feel free to customize with your favorite toppings.