In a fine mesh sieve, rinse quinoa well under cold running water. Drain and set aside.
In a large measuring cup, combine milk and vegetable broth. Heat in the microwave on Medium-High (70 %) for about 3 minutes or until steaming (or heat in a saucepan over medium heat).
Meanwhile, in a large, deep saucepan, melt butter over medium heat. Add onion, red pepper and 1/2 tsp (2 mL) each, salt and pepper and sauté for 5 min or until softened. Stir in frozen vegetables and sauté for 1 min or until starting to thaw. Stir in quinoa and flour. Stir in heated milk mixture and bring to a simmer, stirring.
Reduce heat to low, cover and simmer for 20 min or until quinoa is tender and most of liquid is absorbed. Remove from heat and let stand, covered, for 5 min. Fluff with a fork and season to taste with salt and pepper.