HBO has toyed with Monday nights before. In 2005, the final season of “Six Feet Under” was briefly moved to Monday nights before low ratings prompted executives to put it back on Sundays. The first season of “Enlightened” (2011), the third season of “Bored to Death” (2011) and the second season of “Big Love” (2007) also aired on Monday nights. But those were exceptions.

This time, HBO said, is different.

“It’s not: ‘Let’s see how it does!’” Mr. Bloys said. “This is our new normal.”

He said he and Richard Plepler, the chief executive of HBO, had enacted a plan two years ago to increase the content the network made, a costly but vital move at a time of digital subscriptions and fierce competition from deep-pocketed streaming rivals like Netflix. It was a calculated bet: HBO had a deal in place to be bought by AT&T and hoped its corporate overlords would agree with their plan when they took over.

“The good news is AT&T understood and endorsed the plan to spend money, and going forward into 2021, 2022, we’re going to keep that level of programming up,” Mr. Bloys said. He declined to say how much AT&T had invested in HBO since it became its corporate owner in June.

Other premium cable channels with digital subscription services, like Showtime, have also emphasized the importance of having fresh original programming 52 weeks a year. That way, the thinking goes, when a major hit finishes a season, subscribers will have less reason to cancel their subscriptions.

Even with additional content, HBO’s original programming slate pales in comparison with Netflix. Last year, Netflix earned more Emmy nominations than HBO, snapping HBO’s 17-year streak of garnering the most. They ultimately tied in Emmy wins. But Mr. Bloys emphasized that HBO was not going to grow at the scale of Netflix.

“It’s not just about filling hours,” he said. “It’s just about doing more HBO-level programming.”

HBO has long prized its ability to nurture new talent and be generous with established stars. Some of that talent, however, could perceive a move to Monday night as a signal that their shows are second tier.