In a large mixing bowl add the ground beef, feta cheese, garlic, egg, oregano, sea salt, and freshly ground black pepper to taste.
Squeeze the spinach very well to remove most of the moisture then add it to your bowl. Thoroughly stir to combine this mixture, then form into tablespoon-sized meatballs. I like to use a cookie scoop for this step.
Heat 1 tablespoon of the oil at a time in a large skillet over medium-high heat. Cook half the meatballs turning several times until nicely golden brown on all sides and cooked through about 7-8 minutes. I like to cook them in 2 separate batches to prevent overcrowding.
While the meatballs cook, combine your cooked brown rice or quinoa with your freshly chopped herbs, green onions, lemon zest, fresh lemon juice, and extra-virgin olive oil.
Season with sea salt and pepper to your taste then divide your rice or quinoa mixture equally among 4 meal prep containers.
Top each serving equally with your cooked meatballs, cucumbers, cherry tomatoes, and a dollop of tzatziki, if desired.
Garnish with additional minced herbs if you like then refrigerate for up to 5 days.
This meal prep is excellent served cold.
Enjoy!