It seems to be synonymous with ‘the complete package’, having spread from fast food, where it meant a discount given when you had the full meal, ie hamburger, fries, drink, pudding, etc. to other areas, as in the cites below:
West Side Story is the Full Meal Deal – a movie so strong in so many different areas that it’s impossible to argue with the ‘all-time classic’ label that it’s been given.
ApolloGuide
Student: Don’t just give us the full-meal deal
Zhou notes the common practice of “bundling” textbooks with extras like CDs, software and supplements helps drive up costs.
“Fast food chains promote meals bundling burger and fries, but they also sell the burger on its own. The same principle should be applied to textbook supplements.”
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