MARGIN
Margin in the most basic sense is using money that you borrow from your broker to buy stocks or options. If you have a margin account, your broker will allow you to buy stock with money borrowed from the brokerage. In most cases this increased buying power is used to buy more shares than without margin and not have to pay for them in full. Obviously there are benefits and negatives to trading on margin. Your risk of losing money and borrowed money is greatly increased. You also have a greater ability to make more money as well.

Non-Marginable Securities
Some securities are non-marginable directly from the federal reserve board, while others are declared non-marginable by individual brokerages. The stocks declared non-marginable by the Federal Reserve Board are penny stocks, OTCBB Stocks, pink sheets, and initial public offerings (IPO). Most often the stocks declared non-marginable by your brokerage are stocks that trade under $5.00 or stocks that have extremely high betas. Contact your brokerage for a list of stocks that are non-marginable.

Just to be clear. The answer to the question: Are OTCBB Stocks and Penny Stocks Marginable is a definitive NO!

The reason behind this is simple. The securities classified as non-marginable are high risk. Avoiding margin with them mitigates risk and the costs associated with excessive margin calls. All non-marginable securities must be funded in full with cash and they do not add to your margin buying power.