The company released several productivity and reference software packages during their lifespan, including the highly popular Grammatik grammar checker, for IBM PCs and compatibles running DOS.

[3][6]: 130 In August 1985, RSI released their first product: the Random House Reference Set, a new version of Proofreader for the IBM Personal Computer and compatibles, revised to be a terminate-and-stay-resident program that ran atop other word processors such as WordStar or WordPerfect.

[2] In fall 1988, the company released Grammatik III, a total rewrite that made use of artificial intelligence to more accurately judge the grammar of sentences by breaking them down into a syntactic hierarchy.

[12] By 1989, the product had competitors in Correct Grammar by Lifetree Software and RightWriter by Rightsoft, Inc.[13] By 1990, RSI achieved annual sales of $9.7 million.

[14]: 394 [15]: 76  In March 1992—by which point RSI had sold 1.5 million copies of Grammatik across all versions—the company released version 5 of the program, another rewrite that updated the lexicon further and added new functions such as word redundancy detection.

[16] Around the same time, the company introduced Easy Proof, a pared-down version of Grammatik intended for novice writers, students, and family computers.

[9] In 1991, the company was engaged in a trademark dispute with Systems Compatibility Corporation (SCC) of Chicago, Illinois, over the rights to the Software Toolkit title.

[18] By early 1992, RSI achieved annual sales of more than $13 million, employed 120 people, and had opened international offices in London, Belgium, and Antwerp to sell foreign versions of Reference Set and Grammatik.

[1] On the last day of 1992, RSI received an acquisition offer from WordPerfect Corporation, makers of the namesake word processor based in Orem, Utah.