Three-Tier MOS Selection Process at TBS Is Out

Thanks to the great team at USMC for this guest post.

Most of you have probably heard about the Marine Corps’ three-tier MOS selection process for placing Ground contract officers in their MOS. It’s a historic system that hasn’t changed for decades. Luckily, The Basic School is changing many procedures to better the development and MOS placement of Marine Officers. The Military Occupational Specialty (MOS) is the industry or overall specialty more than the “job” you’ll have at any one given time in Marines. Popular MOSs are infantry, logistics, pilot, artillery officer, and so forth.


Assume there are 90 Marines in a company. Everyone is given a rank from 1 to 90 based on their academic (30%), physical (30%), and leadership (40%) performance.

Those ranks are broken into 3 tiers:

  • first: 1-30
  • second: 31-60
  • third: 61-90TBSStatue_jpg

Each Marine provides a list of their desired MOS in order of preference. The top of each tier from first to third gets priority pick. In the example, the order for picking would be 1, 31, 61, 2, 32, 62, 3, 33, 63, etc. Once your turn to pick comes up they just go down your preference list. If your number one MOS is available you get it, or else they go to your second choice and so on. This means that the person ranking 30 in the company is going to have the third to last pick.

This process was developed in order to ensure “quality distribution.” That is to say that they want to make sure every MOS has a decent spectrum of quality Marines. As you can imagine, the system can be incredibly frustrating given that the 30th Marine gets the 88th pick while the 31st Marine gets second pick. Many times Marines try to “game” the system by failing tests, or physical events, to drop into a lower overall ranking, but ending up at the top of a different tier. The staff will generally catch these acts and respond accordingly.


The historic system in no longer in play. The Marine Corps has developed a new process for placing officers in MOSs. It involves a more hands on approach by the staff. The idea behind “quality distribution” is still very much in play.


Let’s look at the previous example. Instead of breaking the company into thirds the staff will look at the overall average score. For instance, assume the average grade for the company is 85%. Every MOS will be made up of Marines with a sum average that falls between 2.5% of the company average. The average for every MOS would be between 82.5% and 87.5%.

Marines will still submit a preference list, but the staff is going to do everything in their power to get you into one of your top 5 MOSs. In the previous system Marines would end up with the 25th pick on their preference list, since it was a primarily automated process. The Company XO will make the initial determination for placing Marines. Afterwards the entire company staff will get together and SPCs (Staff Platoon Commanders) will trade Marines around. It’s even more critical now for you to constantly talk to your SPC about what MOS you want. When the time comes to trade, if your SPC sees an opportunity to give you what you want then they can do it. At the same time, you have to prove to your SPC that you can do the job you want. If not, your SPC might trade you out of an MOS you wanted because they don’t think your fit for it.

At the end of everything the Company CO will give a final approval. The average distribution rule can be broken if the Company CO approves it. There may end up being a few MOSs where the average grade of the Marines assigned falls out of the 2.5% range.

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5 thoughts on “Three-Tier MOS Selection Process at TBS Is Out

  1. Having been a part of the “old” MOS assignment process at TBS I take exception with the multiple comments about how the Three-Tier System was mostly automated and didn’t take in to account the character and quality of the individual Marine. People will be disappointed in any system, it is statistically impossible to get everyone in their top 5 MOS choices, but we did a pretty good job in the old system. The Marine Corps assigns officer MOSs based on ones propensity to be successful in that MOS, not their desires. Pleading with your SPC is not an endearing character trait. Do you best and the Marine Corps will get you what you deserve, nothing more, nothing less.

    1. Good point, that the old system was not automated, it was divvied up within certain guidelines by the TBS staff.
      Pleading with your SPC has worked in the past but is not the only way.

  2. I have a question. Please excuse me as I am unfamiliar with the terminology. If a person is currently in OCS with a law MOS, can they change their MOS to infantry before TBS or during TBS? If so, who should that person talk to about the change.

    I assume that it cannot be done during OCS as the person has not completed OCS and can be dropped at any point for significant definciences.

      1. Katherine, I asked a Judge Advocate and the short answer is yes. Some people get really motivated at TBS and make the switch.

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