Lohan told Radar Online his deposition lasted approximately two-and-a-half hours and left it doubtful about Gosselin's chances of prevailing in the case.
"I think the attorneys from Williams & Connolly were very thorough," Lohan told Radar Online abut the law firm handling TLC's lawsuit against Gosselin.
"I think they did a great job. They asked the appropriate questions and they got the answers they wanted. I think they have a very, very strong case, one that I definitely don't think they'll lose. So good luck to Jon."
TLC filed the lawsuit against Gosselin in October and has accused him of following through on a threat to end Jon & Kate Plus 8 by suddenly claiming it was "detrimental" to his children after the network refused to release him from an exclusivity contract clause that was preventing him from earning "substantial" money by appearing on other television shows.
Lohan and Gosselin were reportedly working together on the tentatively-titled Divorced Dad's Club reality series, however Endemol -- which is developing the project -- later denied Gosselin's involvement.
According to TLC, Gosselin has been committing "numerous breaches" of the exclusivity clause and violating several other provisions of the April 2008 Jon & Kate Plus 8 contract the family had most recently signed with the network.
"They asked questions regarding my involvement on a business level with Jon Gosselin; deals that were negotiated; transactions that did occur and basically my deal with [Gosselin attorney] Michael Heller," Lohan told Radar Online, adding that he had arranged magazine interviews and "Las Vegas personal appearances" for Gosselin.
"There were some at Ghost Bar, Prive, and the MGM Grand Hotel," he said about the Vegas appearances.
Major was assigned to cover Gosselin as a Star magazine reporter but later claimed to be dating him after the two were photographed having dinner together in New York City and spending time at Lohan's Hamptons home this summer.
During her deposition, Major reiterated her previous claims that Gosselin had also offered to hire her as an assistant as their romance developed.
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"He promised he would [hire me], or else I wouldn't have resigned from my job," she told Radar Online, adding that he told her he'd pay her more than she was making from the magazine.
"I was supposed to be his assistant as well as work with him on a book and other endorsements such as a motorcycle line and a kids clothing line, and kids' stackable furniture."
In addition, TLC's lawyers also asked about her romantic relationship with Gosselin.
"My lawyer intervened so I didn't have to answer any of that," she told Radar Online.
She said his contract with TLC was never a topic of conversation between the pair.
"His contract with TLC never came up," Major told Radar Online. "It didn't seem to concern him."
In addition to Lohan and Major, the case's judge also granted TLC's motion to subpoena Gosselin's "taking a break" girlfriend Hailey Glassman to give a deposition, as well as his attorney Mark Heller, his manager Mark Heller, his bodyguard Thomas Meinelt, and his talent representative Matther Kirschner.
Lohan said Gosselin should be concerned about what Glassman could say during her deposition.
"[Her attorney] has a pretty powerful file, I understand," he told Radar Online.
Gosselin has filed a $5 million counterclaim lawsuit against the network -- claiming TLC hindered his ability to make money by preventing him from working with other media outlets due to an exclusivity clause in his contract with the network.
A preliminary hearing on the two lawsuits will be held on December 10 and address the matter of whether Gosselin's contract should be made public and if TLC can legally prevent him from future jobs in television.
The case is currently scheduled to go to trial on April 19.