Peter Lynch famously said that, "In this business if you're good, you're right six times out of 10." So far, our Rising Star picks are exceeding Lynch's rule-of-thumb guideline, though it's still far too early to make a meaningful assessment of our performance. With two of our picks, Cirrus Logic (Nasdaq: CRUS) and ION Geophysical (NYSE: IO), beating the market by more than 20 percentage points at the moment, however, we are optimistic about the future performance of our recommendations. This week, the Rising Stars made four additional buys, which we've summarized briefly below:

Rising Star Buy: Costco
Rising Star Alyce Lomax selected Costco (Nasdaq: COST) this week for her socially responsible portfolio, urging investors, "Don't sweat the price -- celebrate the philosophy."

Most Foolish investors are probably very well-acquainted with this warehouse retailer. What some investors may not know, however, is that Costco has been very profitable over the past year. Alyce notes that sales are up, earnings are up, and same-store sales are also up. Not only that, but the company boasts a "clean balance sheet, with $4.7 billion in cash and a very reasonable total-debt-to-capital ratio of 17.6%."

Alyce concedes that Costco is not a deeply discounted stock at the moment, but she believes that it's "a gold standard among retailers, and a wonderful stock to own for the long, long haul." For more of Alyce's thinking, have a look at her complete buy recommendation.

Rising Star Buy: Telefonica
Rising Star Jordan DiPietro brazenly dares to be greedy while others are fearful, by purchasing shares of Spanish telecom provider Telefonica (NYSE: TEF). Sure, Spain's economy is very worrying at the moment, but Jordan notes that, "Telefonica was able to increase revenue by 6% during the first nine months of the year."

In the end, Jordan feels that the stock offers a solid dividend along with a "great upside." Read his buy recommendation to hear more about his investing thesis.

Rising Star Buy: Oshkosh
When I saw that Rising Star Jim Mueller had purchased Oshkosh (NYSE: OSK), I immediately thought of children's overalls and that company with the cloying name, "OshKosh B'Gosh." Thankfully, Jim's Oshkosh is not the same one.

Instead, this Oshkosh "builds specialty vehicles like fire engines for airports, cement mixers, personnel lifts, and truck-mounted cranes." Mostly though, the company sells military trucks -- approximately 60% of its revenue is defense-related.

Jim feels that Wall Street is seriously mispricing this company, and he envisions taking an even larger position in it down the road. Read Jim's entire piece to hear his complete thesis. And be sure to thank him for introducing you to the other company from Oshkosh.

Rising Star Buy: Bridgepoint Education
Andy Louis-Charles picked up shares of Bridgepoint Education (NYSE: BPI) this week for his ALOHA portfolio. He also purchased a pair of hip boots as he entered the swamp of the for-profit education sector.

Actually, that was a cheap and unfair shot, which merely furthers Andy's thesis. This industry has received some bad press in recent months (to say the least), but as Andy sees it, "Bridgepoint is an extremely profitable operation run by seasoned industry veterans, offering investors a ton of GULP -- growth at an unreasonably low price."

Andy believes this is an extremely rare opportunity to buy a solid company at a beaten-down price. Read his buy recommendation to hear his case.

Warriors of the working day
In slightly over a month, our Rising Star analysts have selected 30 stocks for their portfolios. Be sure to read the latest buy recommendations above, in addition to all of their other picks . Then stop by and let us know what you think on our boards. We may be just "warriors of the working day," but "by the mass, our hearts are in the trim."

John Reeves owns shares of Costco and always gains inspiration from Act IV, scene 3 of Henry V. Costco is a Motley Fool Inside Value selection and a Motley Fool Stock Advisor pick. The Fool owns shares of Cirrus Logic, Costco, ION Geophysical, Bridgepoint Education, Oshkosh, and Telefonica. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.