Comcast Corp.’s new streaming service Peacock is about to get a big boost from sister movie studio Universal Pictures.

Starting in 2022, theatrical releases from Universal—including the next “Jurassic World” and new “Halloween” movie—will have their TV debut on Peacock, the streamer launched by its parent company last year.

The movies will appear on Peacock no later than four months after their theatrical premiere, joining other studios drastically shortening the length of time they typically wait to make their biggest releases available on the small screen. But it also gives Universal a much-needed advantage over its streaming competitors when every studio’s biggest releases are made available as soon as possible.

By giving its Peacock service greater priority in distribution, Comcast continues its focus on direct-to-consumer offerings that value subscriber growth and retention above all else. Rivals at Walt Disney Co. and ViacomCBS Inc. have taken similar approaches that use marquee titles from a decades-old studio to bolster the appeal of relatively new streaming services. With Wall Street watching for any signs of subscriber losses, studios and their parent companies have broken once-sacrosanct practices to give their services an edge.

While theatrical movies have been strong performers on streaming services, it isn’t clear whether Universal’s move will produce the boost in subscribers it is seeking. Evidence of viewership at most streaming services remains opaque compared with publicly reported box-office tallies, and newer entrants like Peacock have found it hard to siphon viewers from entrenched players like Netflix Inc.

Comcast said in late April that Peacock had 42 million sign-ups. But fewer than 10 million consumers paid for the service as of May, according to a person close to the company. Its buzziest shows so far have included a reboot of “Saved by the Bell” and the comedy “Girls5eva.”

Universal’s ‘F9: The Fast Saga’ was released exclusively in theaters.

Universal’s ‘F9: The Fast Saga’ was released exclusively in theaters.

Photo: Universal/Everett Collection

The deal is a further sign that the big movie and television producers are looking to keep their content in-house to feed their streaming platforms. Peacock has struggled to gain traction against both established streamers such as Netflix and newer entries including Disney’s Disney+ and WarnerMedia’s HBO Max. Universal currently has a deal to send its movies to WarnerMedia’s HBO, but it expires at the end of this year.

However, Universal isn’t quite ready to totally walk away from such lucrative licensing deals to outside companies. The movies it is selling to Peacock will only be exclusive to the platform for four months. Then Universal will make them available to a yet-to-be-determined rival streaming service for 10 months, before the titles revert to Peacock for another four.

With the new terms, Universal Pictures is splitting what is known in the industry as the “pay 1 window” in the anticipation that it can generate more revenue that way and routinely refresh the variety of titles that users see when they open Peacock.

Sony Pictures took a similar approach earlier this year when it struck a deal with Netflix and then Disney for its theatrical movies. Movies will start on Netflix and then migrate to Disney before ultimately returning to Netflix.

The new terms mean that some of Universal’s most important releases will head to Peacock sooner than expected. Universal’s current 2022 slate includes 23 movies, and features sequels to “Puss in Boots” and “Minions,” as well as coming horror movies from director Jordan Peele and the “Halloween” franchise.

In addition to those theatrical releases heading to Peacock, the studio said it would also begin producing movies made exclusively for the service in 2022. The studio declined to comment on the number of films expected to follow this distribution route, but the Peacock-only slate adds to a surge in producing streaming-first movies.

ViacomCBS’s Paramount Pictures employs a similar strategy, with movies made for its theatrical pipeline and its Paramount+ service. Disney and Warner Bros. have taken the two-tier approach, as well.

The moves clarify a film strategy at Universal that has evolved over the past several months in the wake of Covid-19, which closed theaters for more than a year and forced studios to experiment with how and when to put out movies. The studio moved faster than rivals to send would-be theatrical releases to premium video-on-demand services and sign deals with exhibitors that allowed for shortened theatrical distribution.

Since then, it has committed to exclusive theatrical releases with big-budget movies like “F9: The Fast Saga,” while also simultaneously releasing movies like this past weekend’s “Boss Baby” sequel in theaters and on Peacock.

Earlier

The launch of Disney+ has brought a bit of magic to a company whose stock had taken a nosedive after the coronavirus shut down theme parks and movie theaters. WSJ explains how Disney’s streaming platform has become a top competitor in an already crowded field. Photo illustration: Jacob Reynolds/WSJ (Video from 2/9/21) The Wall Street Journal Interactive Edition

Write to Erich Schwartzel at erich.schwartzel@wsj.com and Joe Flint at joe.flint@wsj.com