I cook dinner every night for a 90 year old man. Need tips for shortcuts.

Does he pay you or are you just a friend?

Do you have a slow cooker? Even if you're just fixing vegetables, you can start them cooking before you go to work and then they're done when you're ready. You said he only wants beef once a week, but if he eats chicken, you can put a whole chicken in the slow cooker, then use it for the first meal and pull the meat off for other meals (chicken salad, chicken soup, just plain chicken flavored with lemon pepper or something like that).

Another useful appliance is a George Foreman grill. I have good luck with cooking a portion of chicken quickly that way, or beef or a burger or fish. You can even "roast" vegetables by putting a little oil on them and cooking them in the Foreman as well. My favorite fast food is to take a potato or sweet potato and cook it in the microwave. A potato is delicious topped with broccoli and cheese, or some chili or another thick and hearty soup. If you have done some soup up in advance it would take about ten minutes to get the whole thing done.

While to a 90 years old person, I think he may prefer soft food than hard food. So you can prepare his main food like porridge in the weekends and make sure it stews soft enough for him. Then put it into the fridge. So after coming back from work, you only need several minutes to warm it up by oven. While to the vegatables, it really takes time to clean it up, if you want to save time on it, choose vegetables like tomatoes, cabbages which are easy to wash and you can use them to prepare a salad soon. And the beef for once a week, you can serve it at weekends. I hope it can help, I think you can make it.

Maybe you could fix the meals in advance and freeze them, and just heat them in the oven or nuke them when you are ready to serve and add a salad. Since he doesn't eat much at one time you could maybe spread the veggies out over a few days and add some other ones in between. I have done lots of freezing of meals to be used for future days and it turned out like fresh.

I have worked as a home health aide for over ten years, so I can understand your predicament. I guess it all depends on this man's tastes but I know an ebook that may help. I have no affiliation with this author, but his recipe's can all be made in less then ten minutes, with less than five ingredients, and are pretty healthy. http://thestonesoup.com/blog/images/free_stonesoup_ecookbook.pdf

Sounds like he is leaning more towards being a vegetarian. You could try some Indian recipes they have a lot of vegetable dishes. Also Buddhists are vegetarian. When I lived in Asia I ate at some vegetarian Buddhist restaurants and they were very good. Try googling some Buddhist recipes and see if you can find something simple.