I'm underweight - is this a good daily meal plan for gaining ?

your plan is OK but you aren't eating the right types of foods. for example, I wouldn't have oatmeal because that's what a lot of people on weight loss diets have. if you still want to be healthy, yet gain some weight... maybe for breakfast you could have an egg omelet with veggies inside of it, or waffles with strawberries. Those are more high calorie, yet healthy options. Some other high calorie and healthy foods are avacados, peanut er (PB&J sandwich on wheat), bagels, and many types of seafood. This is some stuff I ate when I was trying to gain weight....cereal, whole milk, peanut er and jelly, cheese, icecream:):) That type of stuff is great for weight gain. I really hope this helped!