In large, nonstick skillet, brown ground beef, breaking apart as you go until completely cooked. Remove from heat and drain. Set aside.
Wipe out pan with a paper towel and place back over the heat. Add olive oil and saute zucchini, squash, corn and black beans, if using. Cook about 5 minutes until veggies start to soften. Add meat back in and sprinkle taco seasoning over. Pour in water and stir. Simmer until water mostly absorbs and you have a moist mixture. Remove from heat.
Microwave frozen cauliflower and white rice together in a large glass bowl until heated through. Stir to mix.
To assemble burrito bowls: scoop some cauli/rice onto your plate. Top with meat mixture and then any desired toppings. Enjoy!