1. Heat olive oil in a large, heavy skillet over medium high heat. Add onion and saute for a minute or two, until it is golden and translucent. Add celery and mushrooms and cook for a minute or two longer, stirring to ensure the veggies do not burn.
2. Add the quinoa and the water, bring to a boil, and then reduce the heat so that everything can simmer for about 15 minutes. Cover the pan during this time.
3. Toward the end of the 15 minutes, add the asparagus and the other vegetables, and cover again. After 15 minutes, turn off the heat and allow everything to sit for 5 minutes. Remove the cover and check to see that all the water is gone and everything is cooked (if not, leave the cover off and simmer for a few more minutes). Season with salt and pepper.