Heat the olive oil in a large saucepan over medium heat. Stir in onions and a pinch of salt and pepper. Cook for 1-2 minutes. Stir in dry couscous. Add in the stock and bring to the boil. Reduce to a simmer, cover, and cook for about 15 minutes, or until the liquid is absorbed. Fluff the mixture with a fork.
In a small bowl mix diced tomatoes and cucumber and set aside.
Divide the couscous into the stainless-steel bowls. Top with the Mexican style 3 beans, corn, avocado, cos lettuce, tomatoes and cucumber, serve with lime wedge.
Eat immediately or seal with the leakproof lid and its ready to go.