Arby's likes to boast in its TV commercials that it has "the meats."

Well, Arby's owner is about to get beefier: It's buying hamburger joint Sonic for $2.3 billion.

Inspire Brands, a private equity backed firm that owns Arby's and Buffalo Wild Wings, is paying nearly 20% more for Sonic than what shares were trading at on Monday.

Sonic (SONC) is famous for its quirky ads and retro 1950s-esque drive-in locations. The company also recently joined the wacky fast food trend of launching odd new menu items with its pickle juice slushies.

But the company has been hit by tough competition from the likes of McDonald's (MCD), Burger King and Wendy's (WEN). Sonic's sales at locations open at least a year have been declining for the past few quarters.

Inspire, which also owns Rusty Taco, said that nothing major will change at Sonic though. The chain, which has more than 3,600 locations, will be operated as an independent brand.

The deal is the latest in what's been a rapidly changing landscape for the fast food and casual restaurants. Struggling chains have decided to sell out or merge to become more competitive.

Roark Capital, an Atlanta-based invesment firm, is the majority owner of Inspire. It has also purchased big stakes in Auntie Anne's, Carvel and Jimmy John's. Just last year Inspire paid nearly $3 billion for Buffalo Wild Wings.

European food giant JAB bought fast casual sandwich chain Panera in 2017 for $7.5 billion. The company, which also owns Krispy Kreme, acquired both Au Bon Pain and Pret A Manger earlier this year.

Burger King parent Restaurant Brands (QSR) scooped up Popeyes Louisiana Kitchen last year while Olive Garden owner Darden (DRI) bought Cheddar's Scratch Kitchen.

There has also been speculation that struggling pizza chain Papa John's (PZZA) could be vulnerable to a takeover.