Slice the avocados in half, removing the seeds. Cut the lemon and rub some juice on the flesh. Dice the cucumber, red onion, and tomatoes; core and dice the pepper and jalapeño; and mince the garlic clove. Prepare the quinoa, per package directions.
Set the avocados aside and add all the diced and minced ingredients, as well as quinoa, in a large mixing bowl.
Add humus and mix everything together.
Fill avocado halves with mixture, topping with salt, pepper, and some lemon juice.