My SO says he’s heard this phrase in advertising a lot lately, and wonders about it. I’d never heard it until he asked about it, then did actually hear it in a car ad. Is it from some movie? Howard Stern? some cutting edge song that’s being played to death? We don’t get out much, so naturally, we’re at a loss. any help?
I couldn’t say where it actually started, but I’ve heard it/seen it in hip hop culture at least as far back as the early 90’s. It seems that a lot of advertisers appropriate underground phrases to get some “street cred” though they never give “props.” Of course, I could attribute the phrase to my Gramma:
“Gramma, which of these Jello deserts is best? The red one, the green with shaved carrots, or yellow with pineapple chunks?”
“Honey, It’s ALL good!”
How about Maxwell House It’s good down to the last drop!, which means it’s ALL good. This of course is not what you are looking for, but it shows that the idea is not original. Maxwell’s phrase will probably still be around, when this one is only a memory. 
And on a related note, Maxwell House’s “Good to the last drop!” slogan was coined by Teddy Roosevelt.
Not sure of the exact origin, but one thing I am sure of is, if I never hear it again, I won’t miss it a bit.
Reeeeally? Cite?
Here’s a cite:
Ah yes, that gawdawful phrase. Obviously in some contexts it is perfectly acceptable, but I have a friend who uses that phrase incessantly, so I’m very sick of hearing it.
If I am trying to put something together (like a social event) and I’m not sure if it will work out, he’ll say, ‘oh, it’s all good!’ Like a glib used car salesman who, when asked about the completely rusted out body of a car s/he’s trying to sell, says, ‘don’t worry, it’s all good!’
No, it’s not.
Key word bolded 
This has nothing to do with the OP…
In 1908 “Good To The Last Drop” was the Coca Cola slogan. They dropped it in 1917. I think Maxwell House picked it up the next year. (No cite and I’m not looking for one.)
Maybe Teddy was talking about coffee. Maybe Coke snuck in and stole the slogan. Dunno.
-Rue.
This is one of those phrases I first heard on SportsCenter and figured they had just made up. Then I started hearing it so many other places, I decided it must have come from somewhere else.
On a similar note, imagine my dismay when I finally got around to watching Swingers and found out that Linda Cohn had not invented the expression “he’s so money and he doesn’t even know it.”
Sportscenter probably has done a lot to popularize the phrase among the mainstream, but they didn’t invent it. I believe the phrase dates back to west coast hip hop slang from close to a decade ago, but I don’t know it’s exact origin. The first verifiable usage I know of it is MC Hammer’s song entitled “It’s All Good” from his 1994 “comeback album” Funky Headhunter (this was two albums after “U Can’t Touch This”, so his success had pretty much evaporated by then). Also, slighty later that same year Notorious B.I.G. used the phrase in his song “Juicy” from the album Ready to Die.