What’s eating investors in Outback Steakhouse? To find out, The Post recently paid a visit — and came away with a plateful of complaints.

The Manhattan location of the nation’s biggest steakhouse chain — whose corporate parent, Bloomin’ Brands, has lately come under fire from activist investors for its lackluster sales — certainly doesn’t seem geared toward New Yorkers in a hurry.

It was 1 p.m. when we arrived at the location on West 23rd Street in Chelsea last week — in other words, peak lunch hour. Maybe the rainy weather explained why the place was almost completely empty when it should have been packed, we thought.

Soon, however, the worries began to stack up like a pile of unwashed plates. Although we were quickly seated at a nearby booth, it took a full 10 minutes for our server to arrive and take our drink orders and ask us if we wanted bread.

At rival steak-and-potatoes chain Texas Roadhouse, it’s a completely different story, according to Barington Capital, a New York hedge fund that is now prodding Bloomin’ Brands to make Outback a better place.

“When customers sit down at their table at Texas Roadhouse, a server immediately presents them with warm, freshly baked bread,” Barington’s James Mitarotonda wrote to Bloomin’ CEO Elizabeth Smith last week.

“We believe this high level of service delights customers and also offers them immediate value,” he added.

Back at Outback, meanwhile, it took another 14 minutes for our appetizer — the chain’s signature, deep-fried “Bloomin’ Onion” — to arrive at our table. It was another 20 minutes before our steaks arrived — again, at a restaurant that was basically empty.

Although we had plenty of time to stare at the walls, there wasn’t much to look at. The supposedly Australia-themed walls were sparsely decorated with what looked like obligatory shots of the Uluru rock formation.

“The 23rd Street restaurant in Manhattan was remodeled in 2014 with additional enhancements in the permitting stage,” a Bloomin’ spokesperson said in an email to The Post.

Our lunch — a 6-ounce sirloin — came with mashed potatoes that tasted like they had been frozen. The steak, which we ordered medium, had no pink in the center, which didn’t surprise us given the wait time. On the other hand, the mac and cheese — not something most people associate with Outback — was surprisingly decent.

At another table nearby, a woman sent back her steak-and-lobster combo, complaining it had arrived cold. It came back 10 minutes later, greeted with silence from the customer.

All of this hints at trouble for Outback as it faces off against not only Texas Roadhouse but also well-regarded rivals including LongHorn, Black Angus and Saltgrass.

“Steakhouses have become highly competitive in recent years,” restaurant consultant Clark Wolf told The Post, noting that there are now many different styles of steakhouse at different price points to appeal to customers.

Meanwhile, “fast and fast casual is so much better than it used to be,” Wolf said. “Without question what [sit-down restaurants] have to do is create an experience.”

Last week, a Chicago-area customer named Sharon told The Post that she rarely visits her local Outback anymore. When she does, it’s often just to pick up a meal to bring home.

“If only there was a restaurant that would treat you like they wanted you to be here instead of, ‘Can we get you in and out of here in an hour?’” Sharon said.

We’d agree, except that it took an hour and four minutes for us to finish our lunch.