Britney Spears brought the “Circus” to an L.A. eatery Wednesday night … exciting patrons of the place when she walked in for food and drinks with her friends.

The singer-songwriter hit up RED O in Thousand Oaks — a suburb of L.A. about 15 miles from the city — standing out in a bright yellow blouse which bared her shoulders, and a fashionable black hat.

Eyewitnesses tell TMZ Britney was in good spirits … complimenting others on their outfits and even taking pics at the bar with a few of her fans.

After enjoying themselves for a bit, Brit was spotted leaving with an assistant holding her hand … before she hopped in her car and drove herself home.

Spears took the opportunity to blow off some steam after a couple weeks of dealing with rumors and the media furor over her ex Kevin Federline‘s new memoir “You Thought You Knew” … in which he made a series of inflammatory claims.

K-Fed accused Britney of using cocaine while she was still breastfeeding her kids, cheating on him with a female dancer on her tour, and calling Justin Timberlake the night before Federline and Spears married.

Spears has denied the book claims in a series of angry social media posts … and, she says K-Fed only wrote it to make money ’cause she hasn’t paid him a single cent in five years — adding, “If you really love someone then you don’t help them by humiliating them.”