Oliver Queen met both Clark and Lois due to his connection to Senator Martha Kent. He started a romantic relationship with Lois and a strong heroic friendship with Clark during Season Six. After his Marriage to Chloe Sullivan (Lois's cousin), Lois became his cousin-in-law and by her (eventual) marriage to Clark, the two heroes became cousin-in-laws.
Lois met Clark after she arrived in Smallville, trying to learn who murdered her cousin, Chloe Sullivan. They started a friendship during Clark's senior year. They didn't have romantic feelings for each other at the time but did care about each other, although they claimed that they couldn't stand each other.
Clark first met Oliver through Lois and initially seemed distrustful of him. Lois sensed the tension between the two and remarked that they need to stop marking their territory and that she wasn't it. While Lois became close to Oliver, she had a clear dislike for Green Arrow, unaware that they were the same person. Clark, on the other hand, soon figured out Green Arrow's true identity.
Lois' investigation into Green Arrow led her to be kidnapped. Green Arrow rescued her, but she showed no gratitude and instead took his bow and arrow and ordered him to reveal his identity. Seeing this, Clark intervened and allowed Oliver to escape. After this, Clark and Oliver built up a friendship and Clark offered Oliver some friendly advice that if he wasn't honest with Lois, their relationship was doomed to fail.
Lois soon began to suspect that Oliver was Green Arrow and she enlisted Clark's help in exposing him. Instead, Clark helped Oliver by dressing up as Green Arrow. After rescuing her from a group of thugs, Lois kissed Clark, thinking that it was Oliver. When Oliver arrived on the scene, Lois realized her mistake and slapped Clark. Later, Lois revealed to Chloe and Clark how much she enjoyed her kiss with Green Arrow and said that he could teach Oliver a thing or two. Clark seemed embarrassed but pleased with himself, while Lois remained unaware that she actually kissed Clark.
Clark's prediction of Oliver and Lois' relationship proved to be correct, as Lois soon tired of Oliver's inexplicable disappearing acts. Lois broke up with Oliver and he left town with his team of heroes.
Lois and Oliver were temporarily reunited when he returned to Metropolis. During his short stay, Lois finally uncovered Oliver's secret identity when Black Canary used her sonic scream, which broke the glass of Oliver's secret closet. Clark arrived at the apartment to check that Black Canary hadn't hurt them. Not realizing that Clark already knew about Green Arrow, Lois tried to hide Oliver's secret identity from Clark, prioritising Oliver over Clark.
Lois was hurt that Oliver kept his identity secret and decided to end their relationship because of his duties as Green Arrow. Clark offered Lois support after her break up and Lois then confessed to Clark that she still loved Oliver but couldn't be with him because she would feel second to his greater destiny. Clark offered Lois a comforting hug. Lois clearly appreciated Clark's support, which brought them closer.
Oliver stayed in Metropolis after finding Clark and Chloe. He respected Lois' decision to end their relationship and didn't try to rekindle their romance. Meanwhile, Lois' relationship with Clark had been growing. Nevertheless, Lois became concerned for Oliver when she heard that he had been poisoned. This made Lois question if breaking up with him was the right choice. Clark seemed a little uncomfortable with Lois' resurgence of feelings for Oliver and reassured her that their break-up was for the best. Lois was relieved that Oliver made a full recovery, although after this they continued to live very separate lives.
Clark and Lois pretended to be engaged to lure out a kidnapper after Chloe and Jimmy became his next victims. During Lois and Clark's pretense they bumped into Oliver in the jewelers. So as not to blow their cover they announced their engagement to Oliver, much to his surprise.
During Chloe and Jimmy's wedding, Lois and Clark almost kissed, but they were interrupted by the arrival of Lana Lang. Clark left Lois to talk to Lana. Oliver found Lois sitting alone and clearly depressed so offered her support, which Lois was initially uncomfortable with. After Oliver's encouragement, Lois confided in him that she had feelings for someone but decided not to reveal who. She admitted that she had never felt this way about anyone before but felt like he didn't need her. Oliver knew immediately that it was Clark and insisted that Clark really did need her. Oliver's friendly support cheered Lois up. At this point Lois and Oliver seemed to finally overcome the awkwardness between them and just see each other as friends.
When Oliver fell into a downward spiral after Jimmy Olsen's death he looked back favorably on his time with Lois. It was apparent that he was still attracted to her when Lois went looking for him for help to escape a Kryptonian assassin. As Clark was missing and she was unable to contact the Blur, she resorted to getting help from Oliver, although he was reluctant to return to his heroic persona.
Oliver eventually returned to Metropolis during an outbreak of a rabid zombie virus. Clark trusted Oliver with keeping Lois safe but she soon became infected and attacked Clark. Nevertheless, Clark was able to hold her until she was cured by the antidote in the rain. Afterwards they embraced each other, relieved to be safe. As Clark and Lois became closer, Oliver faced his demons when the Toyman returned. Clark was keen to support his friend and even sacrificed a date with Lois to save Oliver from committing suicide by apparently stepping off of a pressure sensitive bomb.
Lois was angry with Clark when she discovered that Clark had not told her about Oliver's attempted suicide making it clear she still cared for her ex. She even put herself in danger when she thought Victoria Sinclair had kidnapped Oliver. Seemingly encouraged by Lois' lingering feelings for him, Oliver arranged a blind date with Lois that was being recorded for her new television show. Clark, her new co-host, watched their date on camera and was surprised by Oliver confessing his feelings for Lois. To avoid embarrassment, Lois took Oliver away from where they were being filmed and admitted that she only loved him as a friend now. Oliver correctly predicted that she would rather be with Clark and admired her for knowing what she wants.
The next day, Clark finally made his move and kissed Lois in the middle of the Daily Planet. She then left town for two weeks and Oliver apologized to Clark for going on a date with Lois. After Lois returned, during a conversation in the Daily Planet copy room, she initiated a second kiss with Clark, which ended when her dreams of the future put her in a coma. Oliver and Clark were both concerned for Lois during her coma, especially when she went missing. They worked together to track her down to Belle Reeve. When she woke from her coma, Lois and Clark officially became a couple.
A short time later, Lois was attacked by the Dark Archer, although she assumed that this was Oliver flying into a jealous rage. She ended up in the hospital and was visited by both Clark and Oliver. Chloe had to remind Oliver that it has been a long time since his relationship with Lois and that she has moved on. Oliver knew that Lois had been targeted as she was the only woman that he had really cared about and tracked down his old mentor to defeat him. Despite Oliver's former relationship with Lois putting her in the hospital, Clark remained concerned for Oliver's safety and came to his aid to defeat the Dark Archer. Lois, Clark and Oliver then met up at the Ace of Clubs where Lois smiled at Oliver before leaving with Clark. Oliver was left alone once again.
Oliver consoled Lois when she became jealous of Zatanna's relationship with Clark. Oliver warned Clark that Lois was upset, but Clark seemed surprised that Oliver knew this. Keen to stay with Lois, Clark decided to be honest with her about Zatanna's attempted seduction. Once Lois got revenge by kissing a random passer-by, their relationship was back on track. Meanwhile, Oliver seemed to finally move on from his relationship with Lois when he discussed with Chloe how he always seems to miss out on fun. He then embarked on a relationship with Lois' cousin, Chloe.
Clark came to see Oliver telling him he was considering telling Lois his secret. Oliver told Clark he should do it and that he since he revealed his identity to the public he's felt great like he could be himself. Clark pointed out that when Lois found out Ollie's identity she dumped him. Oliver went on to say that he and Lois weren't meant to be and she loves Clark. Later Clark and Oliver worked together to save Lois from the goddess Isis using her as a vessel and stopping her from unleashing Hell on Earth.
Oliver met with Lois to tell her he was going to register for the VRA. Lois told him it was a really bad idea. Oliver told her that it was the only way to find out what's really going on and said he'd talked Clark out of doing it himself. Lois is surprised that Clark had not told her that he'd been considering it was frustrated that Clark had been communicating with everyone else about it but her. She lamented that she'd thought they'd started having an honest relationship but had now been blindsided. Oliver told her that they needed to keep Clark from trying to act alone to fix the things that might go wrong. Lois was determined to get Oliver back after she found out who was put in charge of the VRA, Slade Wilson, whom had questionable tatics. This led her to met Mera, Arthur Curry's wife. Mera beleived Lois had trouble finding men who suited her life, saying she always goes for stronger, powerful men like AC, Oliver and Clark. Mera beleived she was of lesser quality than those men which Lois shrugged off. After rescuing Ollie, Clark decided to welcome Lois as part of his and Ollie's team at Watchtower. There Clark dicussed the coming darkness on Earth making Oliver and Tess aware of it as well as saying how its using people like Slade and Gordon Godfrey to infect the planet and spread fear and doubt.
Clark was teleported to an alternate universe where he had been raised by Lionel Luthor instead of the Kents. There he saw Lois and Oliver as an engaged couple. Both of them expressed disgust for him as in this universe Lionel raised him to be a murderer. Kent relized he needed the mirror box in order to get back to his universe. Lionel told him Oliver had it. Kent kidnapped Lois from her and Ollie's engagement party and offered Oliver to trade her for the box. While Kent had Lois he tried to convince her that he isn't the Clark she thinks he is and tells her personal information that he knows about her. She seemed to believe it and he left her, promising that he will never let anything like this happen to his relationship with his Lois. Kent then met Oliver at Watchtower. He told Clark that Lois was now safe and had no idea what box he was talking about. He then exposed Kent to kryptonite and was about to kill him until Lionel hit him over the head and revealed that he had the mirror box the entire time. Oliver realized that Clark was the "good one" once he saw Lionel beating him and stopped Lionel as well as turned off the kryptonite. Clark Kent told Oliver to turn on the kryptonite again when Clark Luthor returned and assured Oliver that in the other universe they do save the world together. Kent grabbed the mirror box and activated it. Once he was back in his reality he found Lois and Oliver standing over him about to fire kryptonite weapons at him along with Tess. Kent managed to convince Lois it was really him and Oliver and Tess then lowered their weapons.
Clark and Lois became engaged and Oliver attended their engagement party. During the party, Clark asked Oliver to be his best man, which Oliver proudly accepted. Oliver proposed a toast and congratulated Clark and Lois, saying that he, along with everyone else in the room, knew even before they did that they were destined to be together. Clark and Lois later reminisced about their engagement party when they learned on television about Oliver resisting a citizen's arrest and causing a riot, which the news reporter refered to as a terrorist attack from the vigilantes. Hawkman died as a result of protecting Lois from Slade Wilson. Clark, Lois, Oliver, as well as the rest of the league attended his funeral in Egypt and buried him next to his wife Shayera. As everyone stood over Carter and Shayera's graves in respect, a mysterious white pyramid object rose out of Carter's tomb and flashed a blinding light which rendered the entire team unconscious.
Clark, Lois, Oliver, Chloe, as well as Martha later all celebrated and rejoiced as they learned that the VRA was repealed in a nationwide vote.
Clark Kent was transported back to Earth-2 by Clark Luthor and was at the Smallville Cemetery where a funeral was being held for the Oliver of Earth-2. Ollie and Lois had got married and she placed flowers on his casket and spotted Clark. Kent was then weakened with kryptonite by the AU Lois who said that he had a lot of nerve showing up after he murdered Oliver for revealing his identity as Ultraman as well as exposing his weakness to kryptonite to the rest of the Earth, as well as asked him what it felt like to be the most hated man on the Earth. Kent was able to convince her that he was the "Good Clark" from the other reality. Lois told him that everybody knew about his weakness, as well as that everybody on the planet was armed with kryptonite and that he will be hit on every side, as well as told him to find a way out of this reality as quickly as possible. Kent agreed but said he first had to take care of something as he watched the Jonathan Kent of Earth-2 walk away from the funeral.
Oliver attended Clark and Lois's wedding as the best man. Towards the end of the ceramony, a corrupted Ollie handed Lois and a gold kryptonite ring in order to strip Clark of his powers. As Lois was about to slip the ring on Clark's finger, Chloe spotted the ring and flung it out of Lois's hand and Oliver was revealed to have been corrupted by Darkseid.
A fight between Clark and Oliver then ensued and Lois tried to stop it. Ollie threw her through the air but Clark caught her and saved her. Clark then managed to free Oliver from Darkseid's corruption.