Most often you would interchangeably use either of the following, meaning you had an occasion of consuming the meal at that time.
- I had lunch at two thirty.
- I ate lunch at two thirty.
Now, if you closely looked at the length or speed of the eating action, and wanted to tell the listener that you consumed the food quickly, you would say 4 more often than 3.
- I had lunch quickly.
- I ate lunch quickly.
Then, how about if you are to use 'a quick lunch'? I favor 5, and wouldn't tend to say 6 when careful. Am I on the right track?
- I had a quick lunch.
- I ate a quick lunch.