In a saucepan over medium flame, heat the oil.
Add the onion and cook and stir until the onion is translucent.
Stir in the brown rice and cook so the rice gets a bit brown and begins to crackle.
Stir in the rinsed quinoa and the vegetable broth.
Cover the pan. Allow the grains to come to a boil, and then lower the heat to the lowest setting possible.
Cook without stirring, 35 to 45 minutes. (To check if the liquid has been absorbed or not, tilt the pan to the side.)
Remove from heat and let stand 5 minutes.
With a fork, mix in the parsley, lemon zest and juice.