Rinse the quinoa thoroughly under cold water.

Bring a pot of water to a boil, then add the quinoa. Cook until tender, then drain and set aside.

Heat a drizzle of oil in a pan over medium-high heat. Add the beef mince and cook until browned, breaking it up with a spatula.

Season the beef with ground cumin, salt, and pepper to taste. Stir well to combine.

Add the sliced bell pepper to the pan with the beef. Cook until the pepper is tender-crisp.

Add the spinach leaves to the pan and cook until wilted.

In a bowl, combine the cooked quinoa, beef mixture, and crumbled feta cheese. Toss with lemon juice.

Season the bowl with salt and pepper to taste before serving.