Moving to adopt what has worked for a competitor has helped BATS Exchange gain market share in U.S. equities trading this month, but the immediate results have been less clear for Nasdaq OMX Group (NDAQ) as it tries a similar approach.

At the beginning of June both BATS and Nasdaq OMX launched new order types that route stock trades through private liquidity pools before they're sent onto other exchanges for filling - a practice that has helped Direct Edge, a rival electronic trading venue, boost its share of U.S. stock trading to 12.55%.

BATS officials reported a 1.1% bump in market share for the first five trading days following the June 4 introduction of its new "Bolt" order type, helping the Kansas City-based exchange close the gap with Direct Edge, which unseated BATS as the third-largest U.S. stock trading platform in April.

BATS' U.S. matched market share is currently about 11.1%.

Nasdaq OMX introduced its own version of the so-called "step-up" order type on June 5, dubbed "Flash," but it has yet to show a clear impact on market share.

The New York-based exchange operator's core market share remains flat at approximately 20% month-to-date, while its Boston Stock Exchange unit, which the company has used to introduce a more attractive pricing model, has shown gains, bringing Nasdaq OMX's total U.S. equities market share to about 21.3% month-to-date.

Nasdaq OMX officials noted that the Flash order type has been available on the core Nasdaq market for only eight trading days, and some Nasdaq customers are still coding their systems to access the new order type.

Brian Hyndman, head of transaction services for the exchange, said "we have received a very positive reaction so far."

The Flash order is one of several initiatives pursued by Nasdaq OMX as it looks to reclaim lost ground in a bruising battle for U.S. stock trade.

The exchange has seen its market share fall more than 6% since December, while rival NYSE Euronext (NYX) has also seen business funneled away; its month to date share came in at an estimated 28.5%, down from 34% in December.

NYSE Euronext has objected to the new order types adopted by its rivals, raising concerns around price distortion and investor confidence in a recent letter to the Securities and Exchange Commission.

Still, NYSE Euronext officials haven't ruled out implementing similar practices if competitive pressure warrants.

Chris Isaacson, chief operating officer at BATS, said his exchange is in favor of the SEC evaluating the role of off-exchange trading in U.S. equities market structure, and said its Bolt order type is well within regulations.

"A good healthy market structure discussion is good for the entire industry," Isaacson said. "We're in favor of the most efficient market possible."

William O'Brien, chief executive of Direct Edge, said the flurry of new order types has helped draw attention to his platform, which looks to convert to an exchange by the end of the year.

"All these changes and competitive efforts ultimately help people focus on the fact that how they did business in the past may not be the best way to do it in the future," he said.

-By Jacob Bunge, Dow Jones Newswires; (312) 750 4117; jacob.bunge@dowjones.com