One of my favorite breakfasts (which I don't eat very often because it's too carby for my stupid body) is a serving of cooked oatmeal (150 calories) with a tbsp and a half of peanut butter* (150 calories) and a scoop and a half of vanilla protein powder (70 calories), for a total of about 370 calories with a decent amount of protein and a good serving of fiber.
Most days I do a protein shake on the way to work (I blend half cup milk, half cup water, half a frozen banana, a serving of chocolate protein powder, and a tbsp peanut butter), but not everyone can drink their breakfast and feel satisfied.
For easy, non-processed lunches and dinners, consider tracking down a copy of the South Beach Quick and Easy Cookbook. Just ignore the 'South Beach' bit and check out the recipes; they're all very easy with minimum ingredients, but delicious. I do all my cooking for the week on Sunday night and then just portion things out and microwave. That way it's quick and easy to grab for work or when I'm starving, but I don't have to worry about low protein levels or high salt content. Frozen dinners are convenient and I buy them sometimes, but they never have enough protein to keep me going.
Good luck! You'll figure it out.
*I always spend more to buy the Smart Balance peanut butter with added Omega 3s, a) because I don't get enough Omega 3s in my diet, and b) because it tastes weird right out of the jar and if I have the regular stuff I'll just eat it with a spoon and blow my entire day.