485BPOS

Registration No. 2-75276

File No. 811-3346

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☒
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 70	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 71	☒

Oppenheimer Series Fund

(Exact Name of Registrant as Specified in Charter)

6803 South Tucson Way, Centennial, Colorado 80112-3924

(Address of Principal Executive Offices) (Zip Code)

(303) 768-3200

(Registrant’s Telephone Number, including Area Code)

Cynthia Lo Bessette, Esq.

OFI Global Asset Management, Inc.

225 Liberty Street, New York, New York 10281-1008

(Name and Address of Agent for Service)

It is proposed that this filing will become effective (check appropriate box):

☒ immediately upon filing pursuant to paragraph (b)

☐ on                      pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ on                      pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ on                      pursuant to paragraph (a)(2) of Rule 485.

If appropriate, check the following box:

☐ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of New York and State of New York on the 28th day of February 2019.

	Oppenheimer Series Fund on behalf of its series Oppenheimer Value Fund
By:	Arthur P. Steinmetz*
	Arthur P. Steinmetz
	Trustee, President and Principal Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities on the dates indicated:

Signatures	Title	Date
Joel W. Motley* Joel W. Motley	Chairman of the Board of Trustees	February 28, 2019
Arthur P. Steinmetz* Arthur P. Steinmetz	Trustee, President and Principal Executive Officer	February 28, 2019
Brian S. Petersen* Brian S. Petersen	Treasurer, Principal Financial & Accounting Officer	February 28, 2019
Beth Ann Brown* Beth Ann Brown	Trustee	February 28, 2019
Edmund P. Giambastiani, Jr.* Edmund P. Giambastiani, Jr.	Trustee	February 28, 2019
Elizabeth Krentzman* Elizabeth Krentzman	Trustee	February 28, 2019
Mary F. Miller* Mary F. Miller	Trustee	February 28, 2019
Joanne Pace* Joanne Pace	Trustee	February 28, 2019
Daniel S. Vandivort* Daniel S. Vandivort	Trustee	February 28, 2019
Brian F. Wruble* Brian F. Wruble	Trustee	February 28, 2019
*By: /s/ Taylor V. Edwards Taylor V. Edwards, Attorney-in-Fact

EXHIBIT INDEX

Exhibit     No.	Description
Ex-101.INS	XBRL Instance Document
Ex-101.SCH	XBRL Taxonomy Extension Schema Document
Ex-101.CAL	XBRL Taxonomy Extension Calculation Linkbase Document
Ex-101.DEF	XBRL Taxonomy Extension Definition Linkbase
Ex-101.LAB	XBRL Taxonomy Extension Labels Linkbase
Ex-101.PRE	XBRL Taxonomy Extension Presentation Linkbase Document

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Oct. 31, 2018
Registrant Name	dei_EntityRegistrantName	OPPENHEIMER SERIES FUND
Central Index Key	dei_EntityCentralIndexKey	0000356865
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Feb. 13, 2019
Document Effective Date	dei_DocumentEffectiveDate	Feb. 14, 2019
Prospectus Date	rr_ProspectusDate	Feb. 14, 2019
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A

XML

Oppenheimer Value Fund

<b>The Fund Summary </b>

<b>Investment Objective.</b>

The Fund seeks capital appreciation.

<b>Fees and Expenses of the Fund.</b>

This table describes the fees and expenses that you may pay if you buy and hold or redeem shares of the Fund. You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $25,000 in certain funds in the Oppenheimer family of funds. More information about these and other discounts and sales charge waivers is available from your financial professional and in the section “About Your Account” beginning on page 16 of the prospectus, in the appendix to the prospectus titled “Special Sales Charge Arrangements and Waivers” and in the section “How to Buy Shares” beginning on page 53 in the Fund’s Statement of Additional Information.

<b>Shareholder Fees </b><br/> (fees paid directly from your investment)

Shareholder Fees - Oppenheimer Value Fund	Class A	Class C	Class R	Class Y	Class I
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	5.75%	none	none	none	none
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	none	1.00%	none	none	none

<b>Annual Fund Operating Expenses</b><br/> (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses - Oppenheimer Value Fund		Class A	Class C	Class R	Class Y	Class I
Management Fees	[1]	0.48%	0.48%	0.48%	0.48%	0.48%
Distribution and/or Service (12b-1) Fees	[1]	0.25%	1.00%	0.50%	none	none
Other Expenses	[1]	0.21%	0.22%	0.21%	0.20%	0.04%
Total Annual Fund Operating Expenses	[1]	0.94%	1.70%	1.19%	0.68%	0.52%

<b>Example.</b>

The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in a class of shares of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Any applicable fee waivers and/or expense reimbursements are reflected in the below examples for the first year only. Although your actual costs may be higher or lower, based on these assumptions your expenses would be as follows:

<b>If shares are redeemed</b>

Expense Example - Oppenheimer Value Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	666	859	1,067	1,668
Class C	274	540	931	2,025
Class R	122	380	658	1,452
Class Y	70	218	380	849
Class I	53	167	291	654

<b>If shares are not redeemed </b>

Expense Example, No Redemption - Oppenheimer Value Fund - USD ($)	1 Year	3 Years	5 Years	10 Years
Class A	666	859	1,067	1,668
Class C	174	540	931	2,025
Class R	122	380	658	1,452
Class Y	70	218	380	849
Class I	53	167	291	654

<b>Portfolio Turnover. </b>

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio.

<b>Principal Investment Strategies.</b>

The Fund mainly invests in common stocks of companies that the portfolio manager believes are undervalued. The Fund may also invest in other equity securities, such as preferred stock, rights, warrants and securities convertible into common stock. The Fund may buy securities issued by companies of any size or market capitalization range and at times might increase its emphasis on securities of issuers in a particular capitalization range. While the Fund does not limit its investments to issuers in a particular capitalization range, the portfolio manager currently focuses on securities of larger-size companies.

The Fund may invest up to 25% of its total assets in foreign securities of companies or governments in any country, including in developed and emerging market countries. The Fund may invest up to 10% of its net assets in debt securities.

In selecting investments for the Fund’s portfolio, the portfolio manager looks for companies he believes have been undervalued by the market. A security may be undervalued because the market is not aware of the issuer’s intrinsic value, does not yet recognize its future potential, or the issuer may be temporarily out of favor. The Fund seeks to realize gains in the prices of those securities when other investors recognize their real or prospective worth. The portfolio manager uses a “bottom up” approach to select securities one at a time before considering industry trends. The portfolio manager uses fundamental analysis to select securities based on factors such as a company’s long-term earnings and growth potential. The portfolio manager currently focuses on companies with the following characteristics, which may vary in particular cases and may change over time:

• Attractive valuation,

• Future supply/demand conditions for its key products,

• Product cycles,

• Quality of management,

• Competitive position in the market place,

• Reinvestment plans for cash generated, and

• Better-than-expected earnings reports.

The portfolio manager also monitors individual issuers for changes in their business fundamentals or prospects that may trigger a decision to sell a security, but does not require a decision to do so. The portfolio manager may consider selling a stock for one or more of the following reasons:

• the stock price is approaching its price target,

• the company’s fundamentals are deteriorating, or

• alternative investment ideas have been developed.

<b>Principal Risks.</b>

The price of the Fund’s shares can go up and down substantially. The value of the Fund’s investments may fall due to adverse changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth less than what you paid for them. These risks mean that you can lose money by investing in the Fund.

Risks of Investing in Stocks. The value of the Fund’s portfolio may be affected by changes in the stock markets. Stock markets may experience significant short-term volatility and may fall sharply at times. Adverse events in any part of the equity or fixed-income markets may have unexpected negative effects on other market segments. Different stock markets may behave differently from each other and U.S. stock markets may move in the opposite direction from one or more foreign stock markets.

The prices of individual stocks generally do not all move in the same direction at the same time. A variety of factors can negatively affect the price of a particular company’s stock. These factors may include, but are not limited to: poor earnings reports, a loss of customers, litigation against the company, general unfavorable performance of the company’s sector or industry, or changes in government regulations affecting the company or its industry. To the extent that securities of a particular type are emphasized (for example foreign stocks, stocks of small- or mid-cap companies, growth or value stocks, or stocks of companies in a particular industry), fund share values may fluctuate more in response to events affecting the market for those types of securities.

Risks of Other Equity Securities. Most convertible securities are subject to the risks and price fluctuations of the underlying stock. They may be subject to the risk that the issuer will not be able to pay interest or dividends when due and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Some convertible preferred stocks have a conversion or call feature that allows the issuer to redeem the stock before the conversion date, which could diminish the potential for capital appreciation on the investment. The fixed dividend rate of preferred stocks may cause their prices to behave more like those of debt securities. If interest rates rise, the value of preferred stock having a fixed dividend rate tends to fall. Preferred stock generally ranks behind debt securities in claims for dividends and assets of the issuer in a liquidation or bankruptcy. The price of a warrant does not necessarily move parallel to the price of the underlying security and is generally more volatile than that of the underlying security. Rights are similar to warrants, but normally have a shorter duration. The market for rights or warrants may be very limited and it may be difficult to sell them promptly at an acceptable price. Rights and warrants have no voting rights, receive no dividends and have no rights with respect to the assets of the issuer.

Industry and Sector Focus. At times the Fund may increase the relative emphasis of its investments in a particular industry or sector. The prices of stocks of issuers in a particular industry or sector may go up and down in response to changes in economic conditions, government regulations, availability of basic resources or supplies, or other events that affect that industry or sector more than others. To the extent that the Fund increases the relative emphasis of its investments in a particular industry or sector, its share values may fluctuate in response to events affecting that industry or sector. To some extent that risk may be limited by the Fund’s policy of not concentrating its investments in any one industry.

Risks of Small- and Mid-Cap Companies. Small-cap companies may be either established or newer companies, including “unseasoned” companies that have typically been in operation for less than three years. Mid-cap companies are generally companies that have completed their initial start-up cycle, and in many cases have established markets and developed seasoned market teams. While smaller companies might offer greater opportunities for gain than larger companies, they also may involve greater risk of loss. They may be more sensitive to changes in a company’s earnings expectations and may experience more abrupt and erratic price movements. Small- and mid-cap companies’ securities may trade in lower volumes and it might be harder for the Fund to dispose of its holdings at an acceptable price when it wants to sell them. Small- and mid-cap companies may not have established markets for their products or services and may have fewer customers and product lines. They may have more limited access to financial resources and may not have the financial strength to sustain them through business downturns or adverse market conditions. Since small- and mid-cap companies typically reinvest a high proportion of their earnings in their business, they may not pay dividends for some time, particularly if they are newer companies. Small- and mid-cap companies may have unseasoned management or less depth in management skill than larger, more established companies. They may be more reliant on the efforts of particular members of their management team and management changes may pose a greater risk to the success of the business. It may take a substantial period of time before the Fund realizes a gain on an investment in a small- or mid-cap company, if it realizes any gain at all.

Risks of Value Investing. Value investing entails the risk that if the market does not recognize that a fund’s securities are undervalued, the prices of those securities might not appreciate as anticipated. A value approach could also result in fewer investments that increase rapidly during times of market gains and could cause a fund to underperform funds that use a growth or non-value approach to investing. Value investing has gone in and out of favor during past market cycles and when value investing is out of favor or when markets are unstable, the securities of “value” companies may underperform the securities of “growth” companies.

Risks of Foreign Investing. Foreign securities are subject to special risks. Securities traded in foreign markets may be less liquid and more volatile than those traded in U.S. markets. Foreign issuers are usually not subject to the same accounting and disclosure requirements that U.S. companies are subject to, which may make it difficult for the Fund to evaluate a foreign company’s operations or financial condition. A change in the value of a foreign currency against the U.S. dollar will result in a change in the U.S. dollar value of investments denominated in that foreign currency and in the value of any income or distributions the Fund may receive on those investments. The value of foreign investments may be affected by exchange control regulations, foreign taxes, higher transaction and other costs, delays in the settlement of transactions, changes in economic or monetary policy in the United States or abroad, expropriation or nationalization of a company’s assets, or other political and economic factors. In addition, due to the inter-relationship of global economies and financial markets, changes in political and economic factors in one country or region could adversely affect conditions in another country or region. Investments in foreign securities may also expose the Fund to time-zone arbitrage risk. Foreign securities may trade on weekends or other days when the Fund does not price its shares. As a result, the value of the Fund’s net assets may change on days when you will not be able to purchase or redeem the Fund’s shares. At times, the Fund may emphasize investments in a particular country or region and may be subject to greater risks from adverse events that occur in that country or region. Foreign securities and foreign currencies held in foreign banks and securities depositories may be subject to only limited or no regulatory oversight.

Who Is The Fund Designed For? The Fund is designed primarily for investors seeking capital appreciation. Those investors should be willing to assume the risks of short-term share price fluctuations and losses that are typical for a fund emphasizing investments in stocks. Since the Fund’s income level will fluctuate and will likely be small, it is not designed for investors needing current income. The Fund is not a complete investment program. You should carefully consider your own investment goals and risk tolerance before investing in the Fund.

An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

<b>The Fund’s Past Performance.</b>

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance (for Class A Shares) from calendar year to calendar year and by showing how the Fund’s average annual returns for the periods of time shown in the table compare with those of a broad measure of market performance. The Fund’s past investment performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Sales charges and taxes are not reflected in the bar chart and if those charges were included, returns would be less than those shown. More recent performance information is available by calling the toll-free number on the back of this prospectus and on the Fund’s website: https://www.oppenheimerfunds.com/fund/ValueFund

Sales charges and taxes are not included and the returns would be lower if they were. During the period shown, the highest return for a calendar quarter was 19.46% (2nd Qtr 09) and the lowest return for a calendar quarter was -18.14% (3rd Qtr 11). For the period from January 1, 2018 to December 31, 2018 the return before sales charges and taxes was -11.35%.

The following table shows the average annual total returns for each class of the Fund’s shares. After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes. Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for only one class and after-tax returns for other classes will vary.

<b>Average Annual Total Returns</b> for the periods ended December 31, 2018

Average Annual Total Returns - Oppenheimer Value Fund	1 Year	5 Years	10 Years	(or life of class if less)		Inception Date
Class A Shares	(16.45%)	2.98%	9.60%			Sep. 16, 1985
Class A Shares | Return After Taxes on Distributions	(19.05%)	1.88%	8.90%			Sep. 16, 1985
Class A Shares | Return After Taxes on Distributions and Sale of Fund Shares	(7.87%)	2.34%	7.92%			Sep. 16, 1985
Class C Shares	(12.81%)	3.43%	9.42%			May 01, 1996
Class R Shares	(11.58%)	3.95%	9.98%			Mar. 01, 2001
Class Y Shares	(11.13%)	4.47%	10.60%			Dec. 16, 1996
Class I Shares	(11.00%)	4.66%		8.35%		Feb. 28, 2012
Russell 1000 Value Index (reflects no deduction for fees, expenses, or taxes)	(8.27%)	5.95%	11.18%	9.98%	[1]

[1] Expenses have been restated to reflect current fees.

[1] From 02/29/12

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	OPPENHEIMER SERIES FUND
Prospectus Date	rr_ProspectusDate	Feb. 14, 2019
Oppenheimer Value Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>The Fund Summary </b>
Objective [Heading]	rr_ObjectiveHeading	<b>Investment Objective.</b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund seeks capital appreciation.
Expense [Heading]	rr_ExpenseHeading	<b>Fees and Expenses of the Fund.</b>
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold or redeem shares of the Fund. You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $25,000 in certain funds in the Oppenheimer family of funds. More information about these and other discounts and sales charge waivers is available from your financial professional and in the section “About Your Account” beginning on page 16 of the prospectus, in the appendix to the prospectus titled “Special Sales Charge Arrangements and Waivers” and in the section “How to Buy Shares” beginning on page 53 in the Fund’s Statement of Additional Information.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<b>Shareholder Fees </b><br/> (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	<b>Annual Fund Operating Expenses</b><br/> (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<b>Portfolio Turnover. </b>
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in the annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	45.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you (or you and your spouse) invest, or agree to invest in the future, at least $25,000 in certain funds in the Oppenheimer family of funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 25,000
Expenses Restated to Reflect Current [Text]	rr_ExpensesRestatedToReflectCurrent	Expenses have been restated to reflect current fees.
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>Example.</b>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in a class of shares of the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Any applicable fee waivers and/or expense reimbursements are reflected in the below examples for the first year only. Although your actual costs may be higher or lower, based on these assumptions your expenses would be as follows:
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	<b>If shares are redeemed</b>
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	<b>If shares are not redeemed </b>
Strategy [Heading]	rr_StrategyHeading	<b>Principal Investment Strategies.</b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund mainly invests in common stocks of companies that the portfolio manager believes are undervalued. The Fund may also invest in other equity securities, such as preferred stock, rights, warrants and securities convertible into common stock. The Fund may buy securities issued by companies of any size or market capitalization range and at times might increase its emphasis on securities of issuers in a particular capitalization range. While the Fund does not limit its investments to issuers in a particular capitalization range, the portfolio manager currently focuses on securities of larger-size companies. The Fund may invest up to 25% of its total assets in foreign securities of companies or governments in any country, including in developed and emerging market countries. The Fund may invest up to 10% of its net assets in debt securities. In selecting investments for the Fund’s portfolio, the portfolio manager looks for companies he believes have been undervalued by the market. A security may be undervalued because the market is not aware of the issuer’s intrinsic value, does not yet recognize its future potential, or the issuer may be temporarily out of favor. The Fund seeks to realize gains in the prices of those securities when other investors recognize their real or prospective worth. The portfolio manager uses a “bottom up” approach to select securities one at a time before considering industry trends. The portfolio manager uses fundamental analysis to select securities based on factors such as a company’s long-term earnings and growth potential. The portfolio manager currently focuses on companies with the following characteristics, which may vary in particular cases and may change over time: Attractive valuation, Future supply/demand conditions for its key products, Product cycles, Quality of management, Competitive position in the market place, Reinvestment plans for cash generated, and Better-than-expected earnings reports. The portfolio manager also monitors individual issuers for changes in their business fundamentals or prospects that may trigger a decision to sell a security, but does not require a decision to do so. The portfolio manager may consider selling a stock for one or more of the following reasons: the stock price is approaching its price target, the company’s fundamentals are deteriorating, or alternative investment ideas have been developed.
Risk [Heading]	rr_RiskHeading	<b>Principal Risks.</b>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The price of the Fund’s shares can go up and down substantially. The value of the Fund’s investments may fall due to adverse changes in the markets in which the Fund invests or because of poor investment selection, which could cause the Fund to underperform other funds with similar investment objectives. There is no assurance that the Fund will achieve its investment objective. When you redeem your shares, they may be worth less than what you paid for them. These risks mean that you can lose money by investing in the Fund. Risks of Investing in Stocks. The value of the Fund’s portfolio may be affected by changes in the stock markets. Stock markets may experience significant short-term volatility and may fall sharply at times. Adverse events in any part of the equity or fixed-income markets may have unexpected negative effects on other market segments. Different stock markets may behave differently from each other and U.S. stock markets may move in the opposite direction from one or more foreign stock markets. The prices of individual stocks generally do not all move in the same direction at the same time. A variety of factors can negatively affect the price of a particular company’s stock. These factors may include, but are not limited to: poor earnings reports, a loss of customers, litigation against the company, general unfavorable performance of the company’s sector or industry, or changes in government regulations affecting the company or its industry. To the extent that securities of a particular type are emphasized (for example foreign stocks, stocks of small- or mid-cap companies, growth or value stocks, or stocks of companies in a particular industry), fund share values may fluctuate more in response to events affecting the market for those types of securities. Risks of Other Equity Securities. Most convertible securities are subject to the risks and price fluctuations of the underlying stock. They may be subject to the risk that the issuer will not be able to pay interest or dividends when due and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Some convertible preferred stocks have a conversion or call feature that allows the issuer to redeem the stock before the conversion date, which could diminish the potential for capital appreciation on the investment. The fixed dividend rate of preferred stocks may cause their prices to behave more like those of debt securities. If interest rates rise, the value of preferred stock having a fixed dividend rate tends to fall. Preferred stock generally ranks behind debt securities in claims for dividends and assets of the issuer in a liquidation or bankruptcy. The price of a warrant does not necessarily move parallel to the price of the underlying security and is generally more volatile than that of the underlying security. Rights are similar to warrants, but normally have a shorter duration. The market for rights or warrants may be very limited and it may be difficult to sell them promptly at an acceptable price. Rights and warrants have no voting rights, receive no dividends and have no rights with respect to the assets of the issuer. Industry and Sector Focus. At times the Fund may increase the relative emphasis of its investments in a particular industry or sector. The prices of stocks of issuers in a particular industry or sector may go up and down in response to changes in economic conditions, government regulations, availability of basic resources or supplies, or other events that affect that industry or sector more than others. To the extent that the Fund increases the relative emphasis of its investments in a particular industry or sector, its share values may fluctuate in response to events affecting that industry or sector. To some extent that risk may be limited by the Fund’s policy of not concentrating its investments in any one industry. Risks of Small- and Mid-Cap Companies. Small-cap companies may be either established or newer companies, including “unseasoned” companies that have typically been in operation for less than three years. Mid-cap companies are generally companies that have completed their initial start-up cycle, and in many cases have established markets and developed seasoned market teams. While smaller companies might offer greater opportunities for gain than larger companies, they also may involve greater risk of loss. They may be more sensitive to changes in a company’s earnings expectations and may experience more abrupt and erratic price movements. Small- and mid-cap companies’ securities may trade in lower volumes and it might be harder for the Fund to dispose of its holdings at an acceptable price when it wants to sell them. Small- and mid-cap companies may not have established markets for their products or services and may have fewer customers and product lines. They may have more limited access to financial resources and may not have the financial strength to sustain them through business downturns or adverse market conditions. Since small- and mid-cap companies typically reinvest a high proportion of their earnings in their business, they may not pay dividends for some time, particularly if they are newer companies. Small- and mid-cap companies may have unseasoned management or less depth in management skill than larger, more established companies. They may be more reliant on the efforts of particular members of their management team and management changes may pose a greater risk to the success of the business. It may take a substantial period of time before the Fund realizes a gain on an investment in a small- or mid-cap company, if it realizes any gain at all. Risks of Value Investing. Value investing entails the risk that if the market does not recognize that a fund’s securities are undervalued, the prices of those securities might not appreciate as anticipated. A value approach could also result in fewer investments that increase rapidly during times of market gains and could cause a fund to underperform funds that use a growth or non-value approach to investing. Value investing has gone in and out of favor during past market cycles and when value investing is out of favor or when markets are unstable, the securities of “value” companies may underperform the securities of “growth” companies. Risks of Foreign Investing. Foreign securities are subject to special risks. Securities traded in foreign markets may be less liquid and more volatile than those traded in U.S. markets. Foreign issuers are usually not subject to the same accounting and disclosure requirements that U.S. companies are subject to, which may make it difficult for the Fund to evaluate a foreign company’s operations or financial condition. A change in the value of a foreign currency against the U.S. dollar will result in a change in the U.S. dollar value of investments denominated in that foreign currency and in the value of any income or distributions the Fund may receive on those investments. The value of foreign investments may be affected by exchange control regulations, foreign taxes, higher transaction and other costs, delays in the settlement of transactions, changes in economic or monetary policy in the United States or abroad, expropriation or nationalization of a company’s assets, or other political and economic factors. In addition, due to the inter-relationship of global economies and financial markets, changes in political and economic factors in one country or region could adversely affect conditions in another country or region. Investments in foreign securities may also expose the Fund to time-zone arbitrage risk. Foreign securities may trade on weekends or other days when the Fund does not price its shares. As a result, the value of the Fund’s net assets may change on days when you will not be able to purchase or redeem the Fund’s shares. At times, the Fund may emphasize investments in a particular country or region and may be subject to greater risks from adverse events that occur in that country or region. Foreign securities and foreign currencies held in foreign banks and securities depositories may be subject to only limited or no regulatory oversight. Who Is The Fund Designed For? The Fund is designed primarily for investors seeking capital appreciation. Those investors should be willing to assume the risks of short-term share price fluctuations and losses that are typical for a fund emphasizing investments in stocks. Since the Fund’s income level will fluctuate and will likely be small, it is not designed for investors needing current income. The Fund is not a complete investment program. You should carefully consider your own investment goals and risk tolerance before investing in the Fund. An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	<i>These risks mean that you can lose money by investing in the Fund.</i>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<b>An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.</b>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>The Fund’s Past Performance.</b>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance (for Class A Shares) from calendar year to calendar year and by showing how the Fund’s average annual returns for the periods of time shown in the table compare with those of a broad measure of market performance. The Fund’s past investment performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Sales charges and taxes are not reflected in the bar chart and if those charges were included, returns would be less than those shown. More recent performance information is available by calling the toll-free number on the back of this prospectus and on the Fund’s website: https://www.oppenheimerfunds.com/fund/ValueFund
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance (for Class A Shares) from calendar year to calendar year and by showing how the Fund’s average annual returns for the periods of time shown in the table compare with those of a broad measure of market performance.
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	<i>https://www.oppenheimerfunds.com/fund/ValueFund</i>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund’s past investment performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	Sales charges and taxes are not reflected in the bar chart and if those charges were included, returns would be less than those shown.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Sales charges and taxes are not included and the returns would be lower if they were. During the period shown, the highest return for a calendar quarter was 19.46% (2nd Qtr 09) and the lowest return for a calendar quarter was -18.14% (3rd Qtr 11). For the period from January 1, 2018 to December 31, 2018 the return before sales charges and taxes was -11.35%.
Performance Table Heading	rr_PerformanceTableHeading	<b>Average Annual Total Returns</b> for the periods ended December 31, 2018
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown for only one class and after-tax returns for other classes will vary.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The following table shows the average annual total returns for each class of the Fund’s shares. After-tax returns are calculated using the highest individual federal marginal income tax rates and do not reflect the impact of state or local taxes. Your actual after-tax returns, depending on your individual tax situation, may differ from those shown and after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for only one class and after-tax returns for other classes will vary.
Oppenheimer Value Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	5.75%
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	0.48%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.21%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.94%	[1]
1 Year	rr_ExpenseExampleYear01	$ 666
3 Years	rr_ExpenseExampleYear03	859
5 Years	rr_ExpenseExampleYear05	1,067
10 Years	rr_ExpenseExampleYear10	1,668
1 Year	rr_ExpenseExampleNoRedemptionYear01	666
3 Years	rr_ExpenseExampleNoRedemptionYear03	859
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,067
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,668
2009	rr_AnnualReturn2009	33.65%
2010	rr_AnnualReturn2010	14.70%
2011	rr_AnnualReturn2011	(4.76%)
2012	rr_AnnualReturn2012	13.51%
2013	rr_AnnualReturn2013	30.26%
2014	rr_AnnualReturn2014	10.59%
2015	rr_AnnualReturn2015	(3.81%)
2016	rr_AnnualReturn2016	12.40%
2017	rr_AnnualReturn2017	15.95%
2018	rr_AnnualReturn2018	(11.35%)
Year to Date Return, Label	rr_YearToDateReturnLabel	For the period from January 1, 2018 to December 31, 2018
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Dec. 31, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(11.35%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	19.46%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(18.14%)
1 Year	rr_AverageAnnualReturnYear01	(16.45%)
5 Years	rr_AverageAnnualReturnYear05	2.98%
10 Years	rr_AverageAnnualReturnYear10	9.60%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 16, 1985
Oppenheimer Value Fund | Class C
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Management Fees	rr_ManagementFeesOverAssets	0.48%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.22%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.70%	[1]
1 Year	rr_ExpenseExampleYear01	$ 274
3 Years	rr_ExpenseExampleYear03	540
5 Years	rr_ExpenseExampleYear05	931
10 Years	rr_ExpenseExampleYear10	2,025
1 Year	rr_ExpenseExampleNoRedemptionYear01	174
3 Years	rr_ExpenseExampleNoRedemptionYear03	540
5 Years	rr_ExpenseExampleNoRedemptionYear05	931
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,025
1 Year	rr_AverageAnnualReturnYear01	(12.81%)
5 Years	rr_AverageAnnualReturnYear05	3.43%
10 Years	rr_AverageAnnualReturnYear10	9.42%
Inception Date	rr_AverageAnnualReturnInceptionDate	May 01, 1996
Oppenheimer Value Fund | Class R
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	0.48%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.50%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.21%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.19%	[1]
1 Year	rr_ExpenseExampleYear01	$ 122
3 Years	rr_ExpenseExampleYear03	380
5 Years	rr_ExpenseExampleYear05	658
10 Years	rr_ExpenseExampleYear10	1,452
1 Year	rr_ExpenseExampleNoRedemptionYear01	122
3 Years	rr_ExpenseExampleNoRedemptionYear03	380
5 Years	rr_ExpenseExampleNoRedemptionYear05	658
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,452
1 Year	rr_AverageAnnualReturnYear01	(11.58%)
5 Years	rr_AverageAnnualReturnYear05	3.95%
10 Years	rr_AverageAnnualReturnYear10	9.98%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 01, 2001
Oppenheimer Value Fund | Class Y
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	0.48%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.20%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.68%	[1]
1 Year	rr_ExpenseExampleYear01	$ 70
3 Years	rr_ExpenseExampleYear03	218
5 Years	rr_ExpenseExampleYear05	380
10 Years	rr_ExpenseExampleYear10	849
1 Year	rr_ExpenseExampleNoRedemptionYear01	70
3 Years	rr_ExpenseExampleNoRedemptionYear03	218
5 Years	rr_ExpenseExampleNoRedemptionYear05	380
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 849
1 Year	rr_AverageAnnualReturnYear01	(11.13%)
5 Years	rr_AverageAnnualReturnYear05	4.47%
10 Years	rr_AverageAnnualReturnYear10	10.60%
Inception Date	rr_AverageAnnualReturnInceptionDate	Dec. 16, 1996
Oppenheimer Value Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) imposed on purchases (as % of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as % of the lower of original offering price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	0.48%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.04%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.52%	[1]
1 Year	rr_ExpenseExampleYear01	$ 53
3 Years	rr_ExpenseExampleYear03	167
5 Years	rr_ExpenseExampleYear05	291
10 Years	rr_ExpenseExampleYear10	654
1 Year	rr_ExpenseExampleNoRedemptionYear01	53
3 Years	rr_ExpenseExampleNoRedemptionYear03	167
5 Years	rr_ExpenseExampleNoRedemptionYear05	291
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 654
1 Year	rr_AverageAnnualReturnYear01	(11.00%)
5 Years	rr_AverageAnnualReturnYear05	4.66%
(or life of class if less)	rr_AverageAnnualReturnSinceInception	8.35%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 28, 2012
Oppenheimer Value Fund | Return After Taxes on Distributions | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(19.05%)
5 Years	rr_AverageAnnualReturnYear05	1.88%
10 Years	rr_AverageAnnualReturnYear10	8.90%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 16, 1985
Oppenheimer Value Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(7.87%)
5 Years	rr_AverageAnnualReturnYear05	2.34%
10 Years	rr_AverageAnnualReturnYear10	7.92%
Inception Date	rr_AverageAnnualReturnInceptionDate	Sep. 16, 1985
Oppenheimer Value Fund | Russell 1000 Value Index (reflects no deduction for fees, expenses, or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	(8.27%)
5 Years	rr_AverageAnnualReturnYear05	5.95%
10 Years	rr_AverageAnnualReturnYear10	11.18%
(or life of class if less)	rr_AverageAnnualReturnSinceInception	9.98%	[2]

[1] Expenses have been restated to reflect current fees.

[2] From 02/29/12

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	OPPENHEIMER SERIES FUND
Prospectus Date	rr_ProspectusDate	Feb. 14, 2019
Document Creation Date	dei_DocumentCreationDate	Feb. 13, 2019