no such thing as a zero Rating.
If you play your 1st tournament and lose every game, your starting Rating will be 400 points lower than the average Rating you played ( at least that was the formula years ago ).
For the above formula -- add up all Ratings you played. Divide that by the number of games you played. Then subtract 400. that is your 1st provisional Rating.
At one time, even if you never won a game, your rating couldn't go below 200. I'm not sure if that's still the case, but I'd guess that it is. And all you'd have to do is win a game against an 800-rated player, and your rating would skyrocket. 
Lowest possible USCF rating is 100. I believe post #2 is correct as to how provisional rating is calculated
Forgot about this post. I won one, lost three. My best game was against a 1600, where I was up a pawn but lost on time. It was a very strong field.
if you lose all your games your provisional rating is now calculated by lowest rating-400
also nice job
also nice job
Thank you. It was a rapid tournament, four rounds. Time control of 29 minutes per side, no delay. I saw some people keeping score until it got down to 5 minutes. I want to do that next time. That game I had against my strongest opponent, rated 1600, was very interesting. I was up a pawn, lost on time. He said afterwards that I played well, not blundering. He could have taken one of my pawns, but instead retreated his queen, went for better piece activity and started attacking my isolated d-pawn. I did manage to damage his castle position. Wish we had more time to play. Really nice high school student, and I could sense he was more comfortable and really understood the game, not taking a pawn and wisely spending that tempo to go after the target, my IQP. It started as a Panov Botvinnik, with both of us having IQP’s. He said I would have done better to take his c-pawn early on, giving him the IQP. I’m still learning the theory of the Karo Cann. All in all, I’m glad I attended.
I recently moved to a town where there are real USCF tournaments. I have played these guys in casual games and can’t beat any of them. They are seasoned tournament players with ratings ranging from 1400 to Life National Master. We have an Expert rated player as well.
Question, if I lose every tournament game, very likely, will my provisional rating be zero?
My chess.com rating is 1200, but I feel 400 points lower than the weakest player. I’m not complaining, as they are all giviving me free mini lessons, including the Life National Master, so I do see my game improving. It’s a blast playing with these guys, even if I lose. Playing against an NM in a casual game, I got blown off the board in under 15 moves, but it was a thrill to play with him.