The answer to this question assumes that the foreign country is one of the ~170 countries that are signatories to the Paris Convention. It also assumes that the overseas company’s foreign application doesn’t make a priority claim that is earlier than your own.
In general, so long as you take steps to file a patent application in the foreign country, within twelve months of the date you first filed a patent application for your invention here and claim priority from your original filing, then your foreign patent application will have an earlier priority date than the overseas company’s. Therefore, the overseas company’s application won’t pose a barrier to your foreign patent application.
However, the situation becomes more complicated if the oversease country in question is the USA because the USA used to have a first to invent patent system rather than the first to file system in place in the rest of the world. Consequently, the owners of older US patent applications may have prior rights due to an earlier “conception” of the idea even though they filed later.
When a patent application is examined it is checked to see if the invention that is being claimed is new and involves an inventive step when compared to the prior art base. The prior art base is basically information that was in the public domain, anywhere in the world and in any language, up to the date that the patent application was filed. So, the later the patent application’s priority date, the larger the prior art base will be and the greater the risk that the invention will have already found its way into that prior art base.
This is why it can be risky to unduly delay filing a patent application for an invention.
When you first file a patent application for a particular invention, the date that the application is lodged with the Patent Office becomes the application’s priority date. In some circumstances it’s possible to file a subsequent patent application, for the same invention, so that the subsequent patent application retains the priority date of the first patent application.
This can happen when a provisional patent application is filed as a first application and then subsequently a standard patent application is filed within one year claiming association from the provisional patent application.
Another common situation is when a first patent application for an invention is made in a Paris Convention country and then subsequently the owner of the first patent application files subsequent patent applications in one or more other Paris Convention countries within one year of the first filing.
A patent application consists of:
Since most attention is focused on the patent specification during examination of a patent application, people often tend to refer to the patent application and the patent specification as if they were the same thing.