If you're stopping at the grocery store, swing by the salad bar and pick up shredded greens, sliced green onions and chopped tomato to save prep time.
Boost the vitamin C and the color by adding chopped bell pepper with the onions. Use green bell pepper, or chop a variety of colors of bell peppers.
Canned refried beans come in a variety of types. Look for traditional, fat-free and vegetarian.