Add the lentils into a colander and rinse under water, then transfer into a stock pot, add in 3 cups water (720 ml), and heat with a high heat, once it comes to a boil, place a lid on the pan and lower to a low heat, simmer until the lentils are cooked through (check package instructions, mine took 20 minutes), then drain the lentils into a colander and rinse under cold water, shake off any excess water, and add the lentils into a large bowl

Add the chickpeas into the bowl with the lentils, along with the chopped red onion, chopped red bell pepper, chopped cucumber, sliced black olives, crumbled feta cheese, chopped parsley, and season with salt & pepper, gently mix together

Add the olive oil into a separate bowl, along with the lemon juice, dijon mustard, grated garlic, dried oregano, and season with salt & pepper, whisk together

Pour the dressing over the salad and gently mix together until well mixed, serve at room temperature or even chilled, the salad will hold for up to 3 to 4 days in the fridge, enjoy!