Arby’s Restaurant Group-owner Inspire Brands Inc. said on Tuesday it would buy drive-in chain Sonic Corp. for about $1.57 billion in cash, bolstering its portfolio of restaurant brands that includes Buffalo Wild Wings and Rusty Taco.

Inspire has offered Sonic shareholders $43.50 for each share held, a 19 percent premium to the stock’s Monday close.

Sonic’s shares (SONC.O) were trading just above the offer price at $43.60 in early trading.

Including debt, the deal is valued at about $2.3 billion, the companies said.

Inspire brands was formed by private equity firm Roark Capital as a holding company when Arby’s completed the acquisition of Buffalo Wild Wings earlier this year.

Roark bought a majority stake in Arby’s from Wendy’s Co. (WEN.O) in 2011 and purchased the remaining 12.3 percent last month.