LITCHFIELD—As it marks a rare milestone in the world of fine restaurants this week, 20 years in business overlooking the pretty town green, the widely acclaimed West Street Grill has settled into a happy duality—on the same evening that guests might include Oscar-winning actress Meryl Streep, an ordinary person with good taste can book a table and enjoy a classic bistro entrée, such as moules frites, for just $17.

Co-owners James O’Shea, the irrepressible Irishman, and Charles Kafferman, the dapper and debonair counterbalance, launched their now “legendary boite” with a focus on New American cuisine on May 28, 1990, a time when broadcasting executive and local raconteur William O’Shaughessy judged the historic village to be a “culinary backwater.”

From the beginning, the West Street Grill brought the clubby nature, flair and polished cuisine of a Manhattan restaurant to a region that was just finding and refining its taste for fine dining. While watching chefs come and go, and launching side ventures that included the brief but brilliant trattoria down the street, called Grappa, Mr. O’Shea and Mr. Kafferman nurtured the grill’s reputation as one of Connecticut’s best restaurants, and the place where Litchfield County’s famous residents come to enjoy the food and the sophisticated atmosphere, and to see and be seen in the process.

Notable guests are too numerous to name—Mr. Kafferman once found himself bantering with a walk-in, actor Bill Murray, only to turn around and find himself nose-to-nose with George Clooney—and last weekend was no exception. As a prelude to the actual anniversary date, it was a quietly celebratory time, and in his role as the grill’s unofficial champion—with a (WVOX) radio audience at his disposal—Mr. O’Shaughnessy reported on some of those stopping in to congratulate Mr. O’Shea and Mr. Kafferman on their success.

Actress Susan Saint James and her husband, Dick Ebersol, chairman of NBC Universal Sports & Olympics, were on the list, along with Ms. Streep, Robin Roberts of ABC’s “Good Morning America,” Rex Reed, Broadway legend Patti LuPone, actor and comedian Denis Leary, author Philip Roth and New York attorney Bill Plunkett.

Perhaps the most high profile appearance was turned in by film director Milos Forman—because of his special guest. Joining Mr. Forman was former Czech president Vaclav Havel, a playwright, whose security detail waited outside on the town green.

It’s a life of luster, indeed, at the West Street Grill, and while Mr. O’Shea and Mr. Kafferman appreciate the benefits of a rarefied affirmation from those who could go anywhere, their most passionate focus is the food—and, recently especially, spreading the word that the grill is a warm, welcoming, inclusive place for guests from all walks of life.

Their very talented chef, James Cosgriff, whose cuisine gets better with each visit, is at the center of this redefining of the West Street Grill. A menu that was always seasonal and market based, and always revolved around the finest and freshest ingredients, now takes on bistro and trattoria night incarnations when supremely satisfying dishes are offered for quite reasonable prices.

Dishes like the moules frites are joined by a fistful of pasta du jour dishes, such as sweet sausage and gemelli and homemade fettuccini with confit of garlic, grilled eggplant, roasted peppers, spinach, lemon and extra virgin olive oil. Each of those is just $19.

Steak frites, that French bistro staple, is $23, and caramelized Diver scallops, with Napa cabbage slaw, mango, peanuts, pickled ginger and ponzu sauce are a reasonable $25—more of a steal than reasonable considering that these perfectly cooked, succulent scallops may be the best you’ve had.

West Street’s signature wild salmon burgers, served on homemade brioche with shoestring potatoes and appropriate accoutrements, are just $16.

“Known as one of the great ambiance establishments in the world, The Grill offers all guests a sense of ease and freedom,” public relations consultant Peggy Tagliarino wrote in a release on the grill’s 20th anniversary, pointing to its egalitarian appeal. “It is a welcome respite from the outside world. Stop in and say hello, order a starter, full menu, or a dessert. Come dripping in diamonds or dressed casually. This mix and the mix of people is what make it so much fun.”

The mix of people is definitely fun, but these days who has an urge to look away from the beautifully appointed tables and the dishes that appear before you. The freshest, briniest Connecticut Bluepoint oysters imaginable are in season, and the grill serves six with fresh lemon and a port mignonette for $16.

Even better is the soup de poisson, a pureed version served with saffron aioli and crispy leeks that literally offers up the very essence of every ingredient that went into it. A large and hearty bowl is $12.

Seafood of all stripes is starring at the grill as summer prepares to arrive, and just in is local sea bass that, pan-seared, is a bite of seasonal heaven. Served over dried Roma tomatoes and with braised garbanzo beans, roasted fennel and a tomato-poisson jus, this dish inches into the low $30s but is worth every penny.

The starters on the current bistro menu, meanwhile, are out of this world. Mushroom lovers have to make a reservation at the grill just for the mushroom-and-goat-cheese ravioli ($11), which is served with English peas, cremini mushrooms, shaved grana padano and mushroom jus. Meanwhile, those who have always appreciated the West Street Grill’s incorporation of Asian flavors will love the steamed pork and ginger dumplings ($12), served with cucumber, peanuts, bean sprouts, cilantro, mint and chili-mango sauce.

In what is now a long tenure by Mr. Cosgriff, the grill’s menu has become so accomplished and so catholic in its offerings that any dinner can be a culinary trip around the world. And, as always, that voyage is expertly kept afloat by a stellar wine list. At a recent dinner, for example, the seafood dishes were complemented perfectly by a 2005 Louis Latour Corton-Charlemagne, the noble chardonnay-based white Burgundy. The mushroom ravioli, and other hearty dishes, cozied up to a mature cabernet-based red from the Margaux district of Bordeaux.

The food, the wine, the atmosphere and the incomparable owners add up to 20 years and counting of success, along with so many accolades. “The Grill has a great beckoning charm to it. I’ve been there many times. A country home or weekend place deserves at least one superior dining venue. My friends in the Litchfield Hills are lucky indeed to have a local place like this that reflects an elegant sophistication together with an informal simplicity,” said none other than Sirio Maccioni of Le Cirque.

“West Street Grill is notable not just for serving Litchfield’s notables, but even more so for serving destination-worthy food with unparalleled consistency and hospitality for the past 20 years,” adds Danny Meyer, CEO of Union Square Hospitality Group.

“Food is what made The Grill famous,” says the release on the anniversary. “Food is what continues to make West Street Grill the institution and destination that it is twenty years later. And [Mr.] O’Shea’s desire to continue with the standard and cuisine his passion and palate helped create is now stronger than ever.”

No hype there, just the sweet, simple truth. As the restaurant begins an ongoing year of celebration that will see an ever-changing selection of favorite dishes from the past 20 years appear on the menu, make a date to get in on the excellence that is the West Street Grill.

It is open for lunch and dinner seven days a week. For more information and reservations, call 860-567-3885. The Web site is www.weststreetgrill.com.