Statutory Prospectus Supplement dated July 31, 2020

The purpose of this supplement is to provide you with changes to the current Statutory Prospectus for the Fund listed below:

Invesco Oppenheimer Main Street Mid Cap Fund®

This supplement amends the Statutory Prospectus of the above referenced fund (the “Fund”) and is in addition to any other supplement(s), unless otherwise specified. You should read this supplement in conjunction with the Statutory Prospectus and retain it for future reference.

The following paragraph replaces in its entirety the fifth paragraph appearing under the heading “Fund Summary - Principal Investment Strategies of the Fund”:

The portfolio managers consider stock rankings, benchmark weightings and capitalization outlooks in determining security weightings for individual issuers. Although the Fund mainly invests in U.S. companies, it can invest in securities issued by companies or governments in any country. The Fund primarily invests in common stock but may also invest in other types of securities, such as real estate investment trusts (“REITs”), units of master limited partnerships or other securities that are consistent with its investment objective.

The following information is added under the heading “Fund Summary - Principal Risks of Investing in the Fund”:

Real Estate Investment Trust (REIT) Risk/Real Estate Risk. Investments in real estate related instruments may be affected by economic, legal, cultural, environmental or technological factors that affect property values, rents or occupancies of real estate related to the Fund’s holdings. Shares of real estate related companies, which tend to be small- and mid-cap companies, may be more volatile and less liquid.

Master Limited Partnership (MLP) Risk. An MLP is a public limited partnership or limited liability company taxed as a partnership under the Code. Although the characteristics of MLPs closely resemble a traditional limited partnership, a major difference is that MLPs may trade on a public exchange or in the over-the-counter market. The risks of investing in an MLP are similar to those of investing in a partnership, including more flexible governance structures, which could result in less protection for investors than investments in a corporation. Investors in an MLP normally would not be liable for the debts of the MLP beyond the amount that the investor has contributed but investors may not be shielded to the same extent that a shareholder of a corporation would be. In certain circumstances, creditors of an MLP would have the right to seek return of capital distributed to a limited partner, which right would continue after an investor sold its investment in the MLP. In addition, MLP distributions may be reduced by fees and other expenses incurred by the MLP.

The following information is relocated from under the heading “Investment Objective(s), Strategies, Risks and Portfolio Holdings - Other Investment Strategies and Risks” to under the heading “Investment Objective(s), Strategies, Risks and Portfolio Holdings – Objective(s), Principal Investment Strategies and Risks”:

Real Estate Investment Trusts. The Fund may invest in shares of real estate investment trusts, which are referred to as REITs. REITs pool investors’ funds for investment primarily in income-producing real estate or real estate related loans or interests. REITs can generally be classified as equity REITs, mortgage REITs or hybrid REITs. Equity REITs are companies that primarily invest in real property and derive income mainly from the collection of rents. Mortgage REITs invest the majority of their assets in real estate mortgages and derive their income primarily from interest payments. Hybrid REITs combine the characteristics of both equity REITs and mortgage REITs. REITs are generally not taxed on distributed income if substantially all of its taxable income (other than net capital gains) is distributed to shareholders each year. As a result, REITs tend to pay higher dividends than other types of companies.

Master Limited Partnerships. The Fund may invest in publicly traded limited partnerships known as “master limited partnerships” or MLPs. MLPs issue units that are registered with the Securities and Exchange Commission and are freely tradable on a securities exchange or in the over-the-counter

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market. An MLP consists of one or more general partners, who conduct the business, and one or more limited partners, who contribute capital. The Fund, as a limited partner, normally would not be liable for the debts of the MLP beyond the amounts the Fund has contributed, but would not be shielded to the same extent that a shareholder of a corporation would be. In certain circumstances creditors of an MLP would have the right to seek return of capital distributed to a limited partner. This right of an MLP’s creditors would continue after the Fund sold its investment in the MLP.

O-MSM-STATPRO-SUP

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