Peggy Olson in her birthday outfit on "Mad Men." Photo courtesy of AMC

Dramatically speaking, Season 4 of "Mad Men" has yoyo-ed up and down, with one completely riveting episode usually followed by a good, but not great, one.

Fortunately, last night's was of the former variety, with the plotline keeping us on the edge of our seats for a full hour and, sartorially speaking, we didn't turn off the television unsatisfied, either.

Centered around Peggy Olson's 26th birthday, the episode showed us what the young copywriter wears when she's not all about work, which ends up being a short-sleeved nipped-waist dress in a bold mustard and chocolate brown floral pattern (very Oscar de la Renta) with a little bow on the front.

She pairs the uber-feminine dress with a sea foam green coat, which she wore in a previous episode, featuring a fold-over collar with a light floral print and big gold buttons, a cream colored wool hat, awful orange-hued nylons (hey, it was the '60s!), gold cluster earrings, and a shiny black patent leather pocketbook.

Beauty-wise, this was perhaps the prettiest we've seen Peggy. Her bangs were swept to the side, while her possibly Bump-It-assisted hair was worn half-up and full of flipped ends. (See what we're talking about). Her lips were painted a coral hue (which Joan Harris also rocks) that we are truly coveting.

Speaking of the bodacious Joan, she appears once in the episode, and, in a surprise twist she ditches the vibrant jewel toned dresses for more pared down separates: a flowy bow-neck blouse in a white and light green floral pattern tucked into a high-waisted navy pencil skirt. She punches up the look with the aforementioned lip color and big turquoise button earrings.

The only other female of note that popped up in the episode was Peter Campbell's pregnant wife Trudy who showcases the awful maternity garments of the era, wearing a shapeless cyan skirt suit monstrosity with a silk bow slapped on the front and a sailor collar flapping on her back.

Which lady gets your vote for Best Dressed in Episode 7? Let us know in a comment below.

In related news, see what the women of "Mad Men" wore to the 2010 Emmys in StyleList's red carpet roundup.