What entree would you serve at a party if you're starting with freshly shucked oysters?

beef tenderloin, medium rare

Shrimp etouffee with white rice. A brown roux..onions, celery, bell pepper, parsley and green onion. Finely chopped. Cooked in the roux with oil until translucent. Add Thyme, garlic, bay leaf and chopped tomatoed (drained). Oh..and save the shrimp shells and make a stock out of them before hand (a pressure cooker makes quick work of this).
Add the stock and a cup of white wine. A bit of white pepper, paprika, garlic powder, onion powder, and Worcester sauce. A dash of Tabasco sauce.
Cook that on a slow simmer about 2 hours...adjust season. Add the shrimp at the 30 mins before serving. Simmer that until the shrimp are cooked. Taste and adjust heat/spice and seasoning.
Serve with a 'ice cream scoop' of white rice on a plate surrounded by the etouffee. topped with parsley and green onion bits.

Then a sorbet...followed by a peach cobbler with ice cream and coffee.

Raw oysters and roast pork go unexpectedly well together - I'm thinking of the Bo Ssam at Momofuku. They're served together in that case, but you could just follow your oysters with an entree of Merrill's Sweet & Savory Overnight Pork Roast (same vein) https://food52.com/recipes/28617-sweet-and-savory-overnight-roast-pork or a pork crown roast, or roast loin - stuffed with prunes, with a madeira or port reduction is seasonal and also has a sweet/savory note. Just an idea for a different direction....

def fish. i would do a whole branzino in the oven with fingerling potatoes and cherry tomatoes maybe a bit of capers with lemon and olive oil or stay with the cold / hands-on route and do shrimps (medium sized) with a bit of sea salt and homemade garlic mayonnaise and a fresh baguette. A easier option would be a delicious seafood linguine. Have fun!

I might go with Amanda's Sugar Steak with Bourbon: https://food52.com/recipes/10252-sugar-steak-with-bourbon
Or maybe pan-seared flank steak atop a dollop of pierino's Romesco: https://food52.com/recipes/6452-the-case-of-the-promiscuous-romesco
In either case I'd add some bitter greens, maybe sautéed escarole, maybe grilled radicchio.

How big is your party? How about a simple, silky homemade pasta dish, like carbonara?

From the answers so far, I'm thinking Diamond Jim Brady (famous 19thc New York city eater), so New York steakhouse or British men's club menus. Hope this helps.

Gee, it could be anything you want! However when I first saw your question what came immediately to mind was "Prime Rib!"

For some reason, I'm thinking beef would be good paired with oysters on the half shell. Sort of a surf & turf theme. Maybe grilled or roasted tenderloin & a green salad with some citrus.