B'arzz is a Green Martian, and displays the distinct physical traits common to his species through his armor, including an extremely narrow waist, wide pelvic bones, taloned feet, elongated arms that hang below his knees and three-fingered hands with tapering digits.
The Reach sent scarabs all across the universe to serve as advance agents, and on Mars, it bonded to B'arzz. He was chosen to be a key figure in the invasion of Earth: he would win the trust of the Earth heroes with a story of how he found the scarab as an archaeologist, and discovered it could not control him because of his physiology. He would also come to Blue Beetle's "aid" and offer ways to help him with his problems with the Scarab.
Green Beetle showed up in the fight against Alpha Squad and Black Beetle, and attacked Black Beetle. Alpha Squad did not know who he was, and Black Beetle acted surprised and dismayed.
He initially acquitted himself well in single combat against the Reach enforcer, with his density shifting powers, shape-shifting, and telekinesis giving him an advantage. His distraction, coupled with a psychic link he established, greatly improved the Team's combat effectiveness. Black Beetle reconfigured to blast him with a plasma beam from his back, knocking the Martian into the cornfields. After the beam set the corn alight, Green Beetle's innate vulnerability to fire—despite his armor—left him incapacitated until Impulse extinguished the flames.
Green Beetle instructed Blue Beetle to use his sonic cannon at twenty-seven angstroms precisely. Blue's scarab was adamant the tactic would be ineffectual, but Green Beetle reassured him that although this was normally true, they had double the firepower. The plan worked, forcing Black Beetle to temporarily shut down, and knocking its host unconscious.
Green Beetle levitated both Robin and Arsenal into the air, while Blue Beetle flew off with Impulse, as they beat a hasty retreat to the Kent homestead.
There he explained himself to Nightwing and Alpha Squad; telling them a story about how he found and took control of his scarab, about the scarab's purpose, and why he came to Earth. Over a private psychic link, he also told Jaime he had an alternative to removing his scarab.
The Team took Green Beetle to STAR Labs, where he was introduced to Miss Martian. He told her he was willing to allow her to read his mind and verify his story but Miss Martian was hesitant and Beetle's attempt at a smile made her uncomfortable. Nightwing told them both this was the only way to know that Green Beetle was who he said he was. As Miss Martian established the telepathic link, Green Beetle learned that Miss Martian was really a white Martian and that she had a previous bad experience using her telepathic powers. To ease her mind, Green Beetle volunteered to her his most recent memories. After doing so, Miss Martian told the rest of the Team that Green Beetle was on their side.
Green Beetle then explained to the Team about the Reach fruit drink, saying the additive was designed to addict individuals to the drink and make them placid. Nightwing said the Atom and Flash reached the same conclusion, prompting Green Beetle to wonder why Nightwing still seemed hesitant to trust him. Beetle then further revealed that the additive contained a compound that allowed the Reach to track individuals with the Meta-Gene, which Nightwing realized would allow the Reach a way to weaponize the Meta-Gene. With the briefing completed, Nightwing asked Green Beetle if he needed a place to stay. Taking a human form, Beetle said he would find a place in Taos. After all but Blue and Green Beetle left the room, the two stared at each other.
As the two left STAR Labs, Blue Beetle said he was worried about the prophecy Impulse told him about and asked Green Beetle how he managed to control his scarab. Green Beetle explained that training and meditation would help, but Blue Beetle pressed the issue further. Green Beetle said his Martian physiology and shape-shifting had helped him as well, and when Blue Beetle asked if Green Beetle might be able to use his Martian powers on his Scarab, Green Beetle looked away. Concluding that Green Beetle could help him, Blue Beetle emphasized that he would do anything to have his Scarab silenced.
Green Beetle extended his fingers into the scarab, and successfully rebooted the scarab. Impulse, witnessing the procedure, tried to intervene, but Blue Beetle told Impulse that Green Beetle had been able to silence the Scarab and give him control.
Green Beetle, Captain Atom and Captain Marvel emerged from a portal created by Doctor Fate to assault the Warworld's surface, while Fate defended Earth from its weapons, and Rocket protected Fate. The assault was primary a distraction to allow the Team to infiltrate and shut down the vessel.
When Mongul launched a saturation missile attack, Beetle and the others began destroying as many missiles as they could.
The Warworld May 26, post-12:40 UTC
The Reach sent their fleet to help deal with the missiles, keeping Earth safe for the time being. Beetle and the Leaguers resumed their attack on the Warworld, until the Team succeeded in shutting down the satellite's power core.
Green Beetle was aboard the Warworld with Captain Atom, Doctor Fate and Blue Beetle when Nightwing arrived demanding to know what had happened to the rest of the Team. Blue told him they had been captured with a boom tube on the ground, which he had avoided by flying up. Nightwing ordered Blue to rest; Green Beetle offered to see him home and both Beetles entered a portal created by Doctor Fate.
Green Beetle arrived on the Warworld to help Black Beetle fight Mongul. Together, the two beetles trapped Mongul in a stasis cell as Black Beetle began to discuss the crystal key and its whereabouts. He proceeds to explain the situation to Green Beetle; they are being forced to simply patrol the perimeter around the key chamber because the Ambassador refuses to authorize on attack on the Leaguers guarding the inside of it. Despite him finding it galling, he continues as he lives to serve.
Green Beetles made a dramatic entrance into the temple in Bialya to try and stop the Team from completing the ritual designed to free Blue Beetle. Impulse and Batgirl keep him trapped in a circle of fire, but he phases through the ground and shoots them down. A gecko drops down on top of him and turns into an elephant that crushes him. Weakened but not defeated, Green Beetle flips the transformed Beast Boy over his back and prepares to dissect him. Before he can do so, Bumblebee appears out of nowhere and shoots stingers in his face, Wonder Girl lassos him, and Robin attacks him with a flying kick.
Green Beetle continues to fight as Zatanna furthers the ritual. Green Beetle, along with a controlled Blue Beetle aim their weapons at Zatanna. Zatanna and Isis now unleash a cleansing ritual and Green Beetle discharges his weapon. Impulse grabs the lasso still around Green Beetle's waist and rushes towards Zatanna, placing Green Beetle on the dais near Blue Beetle. As the ritual continues, both beetles are thrown to the ground. A pillar of light emerges from the middle of the dais and engulfs both beetles.
Zatanna soon deactivates their armor to see if the spell has worked, which it has: both B'arzz O'oomm and Jaime gained control of their scarabs once again.
Green Beetle later flew back to Blüdhaven with the rest of the team that went to Bialya.
Green Beetle, Blue Beetle and Aqualad fought their way to the bridge of the Reach flagship while the rest of the Team took out other parts of the ship. The two beetles quickly subdued all the reach agents and the scientist with their staple guns. Aqualad confronted Black Beetle himself, but Black overpowered him and turned his sights to the beetles. Green Beetle attacked him first and used telekinetic powers to force Black Beetle onto the ground. He attached his tendrils to Black Beetle's scarab and tried to reset it, but Black Beetle countered with an attack of his own. Using the attachment between the scarabs, he sent a surge of energy into Green Beetle's scarab and destroyed it. B'arzz collapsed to the ground and Black Beetle prepared to finish him off.
Before Black Beetle could kill B'arzz, however, Blue Beetle blocked the attack. The two beetles fought, and eventually Jaime, united with his scarab, was able to destroy Black's scarab, not without learning the Reach's final plans for the Earth: destroying it.
B'arzz joined 39 other heroes of Earth in a briefing in Metropolis. The heroes would use Lex Luthor's virus to safely disable the disruptors. The heroes were paired off with another into twenty squads: one member would run interference against weapons guarding the disruptors, allowing the other to get close enough to plant the virus.B'arzz was assigned to Epsilon Squad, and worked alongside Nightwing.
Shortly after the Reach invasion ended, B'arzz returned to Mars. On July 4, he called the team requesting their help.