Mince the cloves of garlic and dice the red pepper, celery, and onion in a small dice. Slice the zucchini into rounds and then cut into 4 pieces each for larger chunks.
Add rinsed quinoa, minced garlic, chopped vegetables, marinara sauce, and vegetable broth to the slow cooker.
Turn the slow cooker on to high and cook for 2.5-3 hours (mine was done at 2 hours and 45 minutes).
Remove the lid of the slow cooker and stir the quinoa mixture for 5 minutes to allow any extra liquid to evaporate. If adding spinach (not pictured), dice it up a bit and stir it in during this step.
Turn the slow cooker off and stir in the mozzarella, salt, and pepper until the cheese is fully melted. Adjust spices as necessary.
Recipe by Uproot Kitchen at https://uprootkitchen.com/2015/02/09/crockpot-tomato-vegetable-quinoa-risotto/