I've learned over the years to prep all ingredients ahead of time and put them in separate containers.
This was always requested when we had a luncheon at work.
About 30 mins before lunch, I would put all the ingredients in a bowl (except the fritos) and mix it it all together.
If you buy packaged cubed cheese they see to be too big so I cut them up to smaller pieces. I usually just get an 8 oz block of mild, medium, colby, or sharp cheese and just slice them into small cubes.
Unless you're feeding a lot of people, an 8 oz bottle of Catalina dressing should be fine since the Ranch Style beans provide some liquid also.
When I brought this to work, I usually left the onions and tomatoes in their containers and let them put them in as they wanted. When I make this at home, i mix it all together.
Add Frito's just before serving
Believe it or not, Grandma Mueller loved this!
Variation: If you want to make this more of a 'one dish meal', add some taco meat to the mix.