1. Cook quinoa: In a saucepan, bring water to a boil. Add quinoa, reduce heat to low, cover, and simmer for 15 minutes. Remove from heat and let sit for 5 minutes, then fluff with a fork.
2. Cook mushrooms: In a large skillet, heat olive oil over medium heat. Add sliced portobello mushrooms and cook until tender, about 5-7 minutes.
3. Combine ingredients: In a large mixing bowl, combine cooked quinoa, mushrooms, red bell pepper, red onion, cherry tomatoes, and parsley.
4. Dress salad: Drizzle with lemon juice, season with salt and pepper to taste, and toss to combine.
5. Serve: Serve immediately or refrigerate for later.