Rinse and pat dry the portabello mushroom caps. Flip the caps over and use a spoon to scrape out the brown gills. Proceed to slice the mushrooms into 1/2 inch thick slices.
Placed the sliced mushrooms in a resealable baggie with 2 tbsp of fajita seasoning, 2 tbsp olive oil and the juice of 1 lime. Gently toss until mushrooms are well covered. Let marinate in the fridge for at least 30 minutes.
Cook quinoa according to package instructions. Make enough to yield approximately 4 cups cooked. I like to cook mine in chicken stock for extra flavor.
While the quinoa cooks, cut the onion and bell peppers into 1/4 inch slices.
Place large skillet over medium heat. When hot, add 1 tbsp olive oil. Add portabellos in a single layer making sure not to overcrowd the pan (you may need to cook them in 2 batches). Cook for 4-5 minutes, turning, until tender. Transfer to a plate.
In the same skillet, add remaining tablespoon of olive oil. Add onions and peppers. Sprinkle with 1/2 tbsp fajita seasoning. Cook until tender and slightly charred, approximately 7-8 minutes. Transfer to plate.
To serve, place 1/2 cup to 1 cup cooked quinoa into 4 separate bowls. Divide mushrooms and grilled onions and peppers among the bowls. Garnish with slices of half an avocado, 1 tbsp greek yogurt and your favorite store bought salsa.