TvZ 3OC into Bio

General Overview

This build only builds one Barracks before going straight into three orbital commands.  With this ridiculous economy, you then start very fast upgrades and go straight into Bio play vs Zerg, using your fast Medivacs and early upgrades for constant harass against Zerg.

Build Order

  • 10 – Supply Depot
  • 12 – Barracks
  • 16 – Marine (up to 3)
  • 17 – Orbital Command
  • 17 – Supply Depot (2)
  • 18 – 2nd Command Center
  • 22 – @400 Mins, start 3rd Command Center
  • @300 Mins, start two more Barracks on the low ground of your natural, lift off your first Barracks and finish the 3-Barracks wall-off
    • If your add-ons all end up outside your base, start a 4th barracks in base on which to start your Tech lab for Stimpack and then Combat Shields.
  • @150 Mins, start 2 Refineries
  • @100% Barracks (3 or 4), start Tech lab
  • @100% Techlab start Stimpack Research and 2 Engineering Bays
  • @100% Engineering Bays, start +1 Infantry Attack and +1 Infantry Armor
  • @100 Gas, start Factory and 2 more Refineries
  • @100% Factory, start Starport and Reactor on Factory as well as Armory
  • @100% Stimpack, start Combat Shields
  • Add Barracks as necessary to spend excess minerals
  • @100% Starport, swap onto Reactor
  • @100% +1/+1, start +2/+2 upgrades
  • Double drop as soon as your first two Medivacs pop as you take map control when your barracks start to kick in.  Macro appropriately.


This build is as much as an economical opener as you can have, so you have to be very worried by all Zerg openers; scouting is very important.  With your SCV scout, confirm that your opponent has 15 hatched, and check whether your opponent is getting gas before 3:30 (Metabolic Boost will be researched early; possibility of early roach attacks) or not (lots of queens being made to keep Zerg safe; possibility of very fast 3rd hatch).

Not 15 hatch: Abandon build, stay safe against early roach or bling busts (if your opponent has mined more than 100 gas from their geyser before you SCV dies), and favor 1rax FE into reactor hellion and/or banshee play over your fast third command center.  Keep 2nd CC in base if you are still going to FE until you’ve dealt with their allin.

Gas geyser after 15 hatch: Keep all your units by your natural and try to complete a full walloff ASAP.  Personally, I believe that finishing a walloff with your first 3 barracks (lift off your first one and land it on the low ground) is your best defense because barracks walloffs make banelings more or less worthless.  Bunker up behind this natural barracks wall if you fear bling bust is coming, bunker up at wall if you fear a roach/ling bust is coming.

No gas opener: Poke with your first 3 marines and an SCV to make sure your opponent is not making a very fast 3rd hatch.  If your opponent is making this hatch, try to bunker it in and force a cancel with this attack force.  DO NOT mess up your macro while performing this attack.  If there is no 3rd hatch or your attack is failing, then retreat – leave the SCV at your opponent’s watch tower and the rest of your marines at your own watchtower.  Try to keep that SCV alive to scout for your opponent’s third base timing by moving it between their third and their watchtower (if it’s not down by 8 minutes after no gas opener, suspect roach/bling attack).

Later Roach/Bling attack: Make marauders out of techlabbed barracks, for they are decent against both banelings and roaches.  Focus on making bunkers split around your natural in order to avoid baneling splash.  You should be reasonably safe hiding behind your barracks walloff for a time, but keeping your marines and SCVs alive until those bunkers are down is crucial.  Do NOT clump up those units and have them die to banelings.


As you double drop your opponent, you should be transitioning into full 3 base Bio.  This means that you should float off your third and actually start mining from it, continue your upgrades by getting +2/+2, and make sure your 8ish Barracks are all producing.  Deal with Infestors or Mutas as you scout them by going heavier Marauder or Marine.

Pros and Cons

This build is great because it gives you a ridiculous economy and a very mobile army with which to perform drops and harass your opponent, while you get to freely mass highly upgraded units and expand back at home.  You end up with a highly upgraded and mobile army – your army surges very well as soon as your Barracks kick in as well.

This build is weak against many early game Zerg attacks; however, you will have the strength of a Barracks wall-off to hide behind, so defending is not as dire as you might assume it is.  Also, when you get your first Medivacs out, your Barracks production has not quite kicked in yet, so your army is a lot weaker than you might think in a straight up fight.


  • Build that Barracks wall-off at your natural – otherwise early all-ins will be nearly impossible to defend, and it is a big “good luck busting me” to all Zergs who scout it with an early Zergling.
  • Do whatever you can to hold all-ins – if your opponent kills 30 SCVs, and you still hold, your upgrades and tech mean that you’re still ahead in the game.
  • Try simultaneously dropping the third and main with your first two Medivacs – don’t commit to a straight up engage until your 3rd base has kicked in and your barracks production has followed suit.
  • Don’t miss your upgrades.  Your economy and upgrades are your true advantages when you do this build, you cannot fall behind in upgrades.
  • You cannot afford to build your 3rd outside your main or natural – keep it tucked away in a corner that a sacrificial overlord will be least likely to spot.

Favorable Maps

This build is best on maps where you can fully wall-off your natural with 3 or 4 barracks in order to safely defend early Zerg all-ins.

  • Ohana
  • Cloud Kingdom
  • Condemned Ridge
  • Entombed Valley


MKP doing a similar build vs DRG in the championships of the MLG Winter Arena – Note: this was before Queen range buff, so MKP opens with a 2rax FE into 3OC instead of a 1rax FE.

Mid Masters Example Replay – Note: I overcompensate for not putting SCVs in gas for 10 seconds by getting my 3rd and 4th gas geysers earlier.  Ignore this mistake.

3OC into Bio Tutorial Replay vs a Very Easy AI