- Preheat oven to 350 ºF.
- Cut off the tops of the tomatoes and hollow out the insides.(The pulp can be saved for use in tomato soup or sauce, or salsa).Set tomatoes aside.
- Heat oil in a saucepan over medium-high heat.
- Add onions, and cook until they begin to soften, about 1–2 minutes.
- Add cooked vegetables, and heat through, about another 1–2 minutes.
- Add quinoa, and cook gently until it smells good, about 2 minutes.
- Add chicken broth, and bring to a boil.
- Reduce the heat and cover the pan.
- Cook until the quinoa has absorbed all of the liquid and is fully cooked, about 7–10 minutes.
- When the quinoa is cooked, remove the lid and gently fluff quinoa with a fork.
- Gently mix in the avocado, pepper, and parsley.
- Carefully stuff about ¾ cup of quinoa into each tomato.
- Place tomatoes on a baking sheet, and bake for about 15–20 minutes, or until tomatoes are hot throughout (tomatoes may be stuffed in advance and baked later).
- Serve immediately.