Meal replacement bars will not have enough fat, carbs or total calories. If you are in shape and working out you likely need 3000 to 4000 calories a day. I have 3 balanced meals a day (each meal has grain, vegetable, meat/eggs, fruit and dairy) plus a post workout meal (whole milk, whey protein, dextrose, fudge, banana) and an evening snack (oatmeal, peanut butter, whey protein and whole milk).
Preparing meals does not have to be time consuming, especially if you get into the rhythm of making the same set of meal everyday. Cooking meats in a cast-iron skillet only take a few minutes. Cooking fresh vegetables including diced sweet potatoes only takes 3 to 4 minutes in a microwave. Rice and quinoa, take 20 minutes, but you can make several days worth at a time.