I take a basic salad and add some cherry tomatoes and grilled chicken. Costco has packs of grilled chicken strips that work perfect for adding to salads. I carry a vinaigrette dressing in a separate container.
Lately I've been making a breakfast casserole that includes ground turkey, sweet potatoes, spinach and eggs that makes enough to last me the week. It's really good. It could also be used as a snack to carry with you.