There are so many good restaurants in the Union Square area recommend Googling top 10 restaurants in Union Square. Absolutely the best place is Taj Campton Place one-star Michelin.
There's a few you can choose from, it depends on what you are in the mood for. Italian, Indian, American or etc.
Zingari in the hote Doninatelo. is one block above the Grary at Post st
For Italian, I like Scala's on Powell between Post and Sutter. For American, try John's Grill on Ellis between Powell and Stockton.
The theater is by Union Square so there are many restaurants around at all price points and many ethnicities. If you're going to a restaurant, and not a diner, be sure to make reservations with adequate time allowed since you won't be the only ones dining before the show.
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