NEW YORK ( TheStreet) -- Mortgage servicing companies such as Ocwen Financial ( OCN - Get Report) and Nationstar Mortgage Holdings ( NSM) have posted stellar stock prices over the past couple of years as they have picked up market share from the big banks, but Oppenheimer & Co. analysts say the "secular shift" benefiting the servicers is still "in the early-to-middle innings."

Oppenheimer initiated coverage on both Ocwen and Nationstar with "outperform" ratings after Monday's market close. The analysts also began covering PHH Corp. ( PHH) and Walter Investment Management ( WCS), which they rate "perform," stating "it is more valuation than anything else that holds us back."

Investors appeared to take heed of the report, driving up shares of Ocwen and Nationstar by more than 2% each in the first 45 minutes of trading, while shares of Walter and PHH were flat to lower.

All four companies have grown market share dramatically since 2009 when the servicing industry was dominated by Bank of America ( BAC - Get Report), Wells Fargo ( WFC), JPMorgan Chase ( JPM) and Citigroup ( C). Those companies had 55.9% of the servicing market in the first quarter of 2009, a number that fell to 44.1% in the second quarter of 2013, according to Oppenheimer. Ocwen, Nationstar, PHH and Walter, meanwhile, have gone from virtual non-entities to control a combined 11.1% of the market.

Mortgage servicers collect debt payments from homeowners, receiving fees of about 0.25% on outstanding unpaid principal. The right to collect the debts and charge the fee is known as a mortgage servicing right (MSR). While Ocwen, Nationstar and Walter posted $2.1 billion in combined servicing revenues in 2012, Oppenheimer sees another $2.5 billion to $3.5 billion in revenues up for grabs in the next 12 to 36 months as banks sell servicing rights on an additional trillion dollars' worth of mortgages.

The big banks have been moving out of the servicing business due to litigation arising from issues such as "robosigning" and other mishaps. New capital rules also make it more expensive for them to hold servicing assets.

In addition to opportunities to grow revenues by purchasing MSRs, Oppenheimer's analysts believe originating new mortgages will enable servicers to grow their portfolios further. They also see opportunities for the servicers to reduce funding costs and work with "strategic partners" to enable them to make large MSR portfolio acquisitions, among other advantages.

-- Written by Dan Freed in New York.

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