Heat oven to 400℉.
Spread cooked quinoa in the bottom of a 9-inch square glass pan.
Heat a cast iron skillet on medium heat and use the olive oil to pan sear both sides of the chicken tenders. Remove pan from heat. Remove chicken from pan and set in four rows on top of quinoa.
Spread the broccoli florets over the top of the chicken and quinoa in the baking dish.
In a small bowl, mix the flour and the chicken seasoning together. Stir into remaining oil in the pan. Use a fork to stir and mix well. Set pan back on low heat.
Add the milk and the water to the flour mixture and blend well to make a sauce. Stir and cook the sauce until it thickens and bubbles. You can raise your heat a little to cook it quicker, but keep stirring mixture so it does not burn to pan.
Once sauce bubbles, lower heat and add the cheese. Stir until the cheese is melted and blended.
Pour cheesy sauce over broccoli, chicken, and quinoa in pan.
Bake at 400℉ for 25 minutes.